Skip to content

Clinicians › Knee

Quadriceps and patellar tendon rupture

58 citationsUpdated Oct 2026
Illustration: knee

For patients: a plain-language version of this topic is available. See the patient guide.

Overview

Patellar and quadriceps tendinopathy affects active individuals engaging in forceful eccentric knee extension, with patellar involvement predominating in adolescents and young adults and quadriceps involvement in older populations [22]. The condition arises from repetitive stress on the extensor mechanism, particularly in jumping sports on hard surfaces [22]. Pathoanatomy involves degenerative changes such as fibrinoid necrosis and mucoid degeneration, most frequently at the deep fibers of the patellar attachment where blood supply is tenuous [22]. Clinically, patients present with insidious pain and swelling that progresses from post-activity discomfort to functional limitation during activity [22]. Physical examination reveals tenderness at the tendon-bone interface and discomfort with resisted extension, while MRI demonstrates tendon thickening, which is more diagnostic than signal abnormalities [22].

Operative intervention is indicated for extensor tendon ruptures where function is compromised and soft tissues are adequate for healing, as well as for tendinopathy refractory to nonsurgical management [19, 22]. Nonsurgical treatment remains the mainstay for tendinopathy, utilizing activity modification, eccentric strengthening, and NSAIDs, while corticosteroid injection is contraindicated due to rupture risk [22]. Acute repair techniques vary by lesion type but generally aim to restore the extensor mechanism, with early surgical management essential to prevent the challenging reconstructions associated with delayed treatment [2, 6]. Good to excellent outcomes are reported in both quadriceps and patellar tendon rupture groups, though acute quadriceps repair may yield superior knee function compared to patellar tendon restoration [1, 7].

Special considerations include total knee arthroplasty and ACL reconstruction contexts. In post-arthroplasty ruptures, suture anchor fixation is a viable option, though patients must be counseled on high reoperation and infection rates, with direct patellar tendon repair associated with a 63% poor outcome rate [65, 71]. Following ACL graft harvest, rare patellar tendon ruptures typically occur in a proximal-medial/distal-lateral pattern, favoring immediate primary tendon repair and delayed ACL reconstruction [8, 17]. Chronic ruptures may require reconstruction using autografts or allografts, particularly when soft tissue coverage or bone stock is inadequate [3, 5, 31, 60, 67].

Anatomy & Pathophysiology

Soft Tissue Anatomy

The extensor mechanism comprises the quadriceps tendon, medial and lateral retinacula, patella, and patellar tendon [111]. The quadriceps muscle complex consists of the vastus lateralis, vastus medialis, rectus femoris, and vastus intermedius [111]. The vastus lateralis inserts on the patella at an approximately 30-degree angle relative to the longitudinal axis of the femur [111]. The vastus medialis longus inserts proximally on the patella at an angle of 15 to 18 degrees relative to the femoral long axis, while the vastus medialis obliquus inserts more distally at an angle of 50 to 55 degrees [111]. Rectus femoris fibers run 7 to 10 degrees medially relative to the femoral long axis in the coronal plane [111]. The vastus intermedius lies deep to the rectus femoris and inserts directly into the superior base of the patella [111].

The quadriceps tendon has been described as having two to four distinct layers [28]. Previous studies report a trilaminar organization, with the rectus femoris tendon superficial, the vastus medialis and lateralis tendons in the middle, and vastus intermedius fibers deep [111]. The insertion reflects an intricate blending of all tendon fibers at the superior patella [111]. The patellar retinaculum and iliotibial band function as secondary extensors of the knee [111]. The retinaculum forms from the continuation of the deep investing fascia lata in the thigh and is reinforced by inserting aponeurotic fibers from both the vastus medialis and lateralis [111]. Both the medial and lateral retinacula insert directly into the proximal tibia [111].

The medial patellofemoral ligament (MPFL) is an extracapsular continuation of the deep retinacular surface of the VMO, extending from the superior medial border of the patella to bone just anterior to the medial collateral ligament on the medial epicondyle [111]. It contributes 50% to 60% of the total restraining force of the medial patellar stabilizers [111]. The MPFL has a fan-shaped configuration running from the upper medial margin of the patella to a femoral insertion posterosuperior to the epicondyle and just distal to the adductor tubercle [111]. Cadaveric dissections reveal the MPFL to be 58.8 ± 4.7 mm in length, 12 ± 3.1 mm in width, and inclined 15.9 ± 5.6 degrees proximally [111].

The patellar tendon originates from the apex of the patella proximally and inserts into the tibial tubercle distally [111]. Its average length is 5 cm [111]. The patellar tendon forms primarily from a continuation of the central fibers of the rectus femoris tendon [111]. It is reinforced at its tibial insertion medially and laterally by the extensor retinaculum and the iliotibial tract [111]. The patellar tendon receives its blood supply from the infrapatellar fat pad and from the retinaculum through the medial and lateral inferior geniculate arteries [62].

Pathophysiology & Mechanism of Injury

Rupture of the patellar or quadriceps tendon generally occurs with eccentric loading of the knee extensor mechanism, often when the foot is planted and the knee is slightly bent [28]. Less commonly, these injuries occur with a direct blow to the tendon when the extensor mechanism is under tension [28]. These are typically low-energy injuries [36]. The patient typically sustains a forceful quadriceps contraction against a fixed or sudden load of full body weight with the knee in a flexed position, resulting in eccentric loading [36]. The rupture typically occurs during an eccentric load on a flexed knee, such as landing from a jump or taking a forceful step while descending stairs [28]. Less commonly, a rupture can occur during a forceful quadriceps contraction when taking off for a jump [28].

In general, healthy tendons do not rupture [96]. Under normal conditions, tensile overload of the extensor mechanism usually leads to fracture of the patella, which is considered the weakest link in the extensor mechanism [96]. In a rabbit model, between 50% and 75% of the tendon fibers had to be transected to result in a rupture under forces greater than those seen under physiologic conditions [96]. It takes over 17 times body weight to rupture a normal patellar tendon, whereas the patellar tendon routinely sees forces of 3 times body weight when ascending stairs [62].

Patellar tendon ruptures secondary to indirect trauma have been considered the end stage of long-standing chronic tendon degeneration secondary to repetitive microtrauma [96]. Biopsy specimens of spontaneously ruptured tendons reveal pathologic findings that are degenerative in nature, including hypoxic tendinopathy, mucoid degeneration, tendolipomatosis, and calcifying tendinopathy [96]. Ruptures may occur in the absence of pathologic tendon degeneration [96]. The frequent prevalence of prodromal symptoms associated with tendon failure seems to support the finding of tendon degeneration prior to rupture [96]. Prodromal symptoms were present in 46% of professional football players prior to patellar tendon rupture [96].

Both patellar tendon and quadriceps tendon ruptures typically occur at the tendon attachment to the patella [28]. Underlying chronic degeneration often is present and is characterized by angiofibroblastic tendinosis, mucoid degeneration, and pseudocyst formation at the attachment of tendon to bone [28]. The area of patellar tendinopathy has a tenuous blood supply [22]. Affected tissue in patellar tendinopathy may demonstrate fibrinoid necrosis, angiofibroblastic change, or mucoid degeneration and disorganized collagen structure [22]. The medial portion of the patellar tendon often demonstrates thickening compared with the rest of the tendon in tendinopathy [22].

Demographics and Predisposing Factors: Rupture of the patellar tendon is most common in patients younger than 40 years [28]. Patellar tendon ruptures occur more commonly in patients less than 40 years old, while quadriceps tendon ruptures occur more commonly in patients greater than 40 years of age [36]. Patellar tendon ruptures are most common in the third and fourth decades of life and more common in males than females [62]. A 5.6 to 1 male to female ratio was found for patellar tendon ruptures [15]. The average age at time of rupture was 36 for patellar tendon ruptures and 51 for quadriceps tendon rupture patients [15].

Patients who sustain quadriceps tendon ruptures may have underlying conditions that predispose them to injury, such as obesity, diabetes mellitus, hyperparathyroidism, rheumatoid arthritis, systemic lupus erythematosus, hyperbetalipoproteinemia, hemangioendothelioma, chronic renal failure, or gout [28]. Risk factors for patellar tendon rupture include systemic lupus erythematosus, rheumatoid arthritis, chronic renal disease, diabetes mellitus, steroid injection, and preexisting patellar tendinopathy [62]. Anabolic steroid use and local corticosteroid injection into the tendon also are associated with both types of tendon ruptures [28].

Injury Patterns and Associated Injuries: The most common injury pattern for patellar tendon rupture is a proximal sided rupture [62]. Midsubstance ruptures or distal avulsions of the patellar tendon are also possible [62]. A complete patellar tendon rupture occurs in 97% of cases reported in the literature and usually occurs at the pole of the patella [124]. ACL tears have accompanied up to 12.5% of high-level sporting injuries resulting in patellar tendon rupture [36]. A 30% incidence of intra-articular associated injuries was found in all patients with patellar tendon rupture [15]. The most common associated injuries in the patellar tendon rupture group were ACL ruptures (18%) and medial meniscus tears (18%) [15]. Eight patients had either a medial tear, lateral tear or both meniscuses torn (24%) in the patellar tendon rupture group [15].

Numerous reports of simultaneous bilateral quadriceps tendon rupture have been published and include patients with systemic illness and obesity [36]. Bilateral rupture of the patellar tendon can occur but is less frequent [36]. Patellar tendon rupture also has been reported after midthird tendon harvest for knee ligament reconstruction [28].

Indirect injuries to the patella occur secondary to the large forces generated through the extensor mechanism, and typically result from forceful contraction of the quadriceps with the knee in a flexed position [110]. The substantial force generated by a violent quadriceps contraction fractures the patella and may propagate through the adjacent retinaculum of the extensor mechanism [110]. Indirect injuries frequently cause a greater degree of retinacular disruption compared with direct injuries, and active knee extension is compromised in most cases [110]. Most patella fractures have a transverse fracture pattern, resulting from excessive tensile forces through the extensor mechanism [110]. Small proximal or distal avulsion-type fractures of the patella are often associated with substantial soft tissue injury to the quadriceps or patellar tendon [110].

The shortening of the patellar tendon correlates with the severity of the patellofemoral osteoarthritis [32]. The altered function of the patellar tendon in anterior cruciate ligament deficiency resulted in an altered patellar tracking and patellofemoral cartilage contact [113]. Concurrent increases in patellar tendon and ACL strains indicate that the quadriceps load the ACL via the patella tendon when the knee is positioned near extension [134]. The central third of a non-irradiated, human bone–patellar tendon–bone construct is thicker and biomechanically superior to the medial and lateral regions in most respects [114]. Based on mechanical tensile properties analyses, the quadriceps tendon-bone construct may represent a versatile alternative graft in primary and revision anterior and posterior cruciate ligament reconstruction [131].

Classification

Blazina: The Blazina classification applies to patellar or quadriceps tendinopathy and consists of three stages. Stage 1 is defined by pain after activity, Stage 2 by pain during and after activity, and Stage 3 by pain that limits function during an activity [22].

Partial Patellar Tendon Tear: A classification system for partial patellar tendon tears is based on tendon anterior-posterior thickness and the percentage of tendon torn, demonstrating high interrater and interobserver reliability [53]. The Popkin and Golman classification for these tears assists in treatment decision making, with surgical débridement and possible repair recommended for grade 4 tears that fail 6 months of conservative treatment [53].

Post-ACL Graft Harvest: Patellar tendon ruptures occurring after ACL graft harvest typically present in a proximal-medial/distal-lateral or entirely distal pattern [17].

Medial Patellofemoral Ligament: The severity of medial patellofemoral ligament tears is classified as full thickness, high-grade partial, or partial thickness based on shape and signal abnormality observed on axial fat-suppressed, intermediate-weighted MRI sequences [154].

Other Considerations: The average age at time of rupture is 36 for patellar tendon ruptures and 51 for quadriceps tendon rupture patients [15]. Patellar tendon ruptures are more common in males, with a male to female ratio of 5.6 to 1 [15]. In pediatric populations, patellar tendon rupture represents 7% of patients who sustained acute traumatic injury of the knee extensor mechanism [29].

Clinical Presentation

Mechanism and Epidemiology

Patellar tendon ruptures occur more frequently in males, with a male-to-female ratio of 5.6 to 1 [15]. The injury is rare in the pediatric population, representing 7% of pediatric patients who sustain acute traumatic injury to the knee extensor mechanism [29]. In high-level athletes, the mechanism of injury is typically an eccentric overload on a flexed knee, as documented in 21 of 24 injuries within a National Football League cohort [57]. Both patellar and quadriceps tendon ruptures are associated with anabolic steroid use and local corticosteroid injection into the tendon [28].

History and Symptoms

Patients often report a history of pain consistent with underlying tendon degeneration [28]. The acute injury is dramatic, characterized by pain with an associated tearing or popping sensation, followed by swelling and an inability to bear weight [36, 54]. Prodromal signs and symptoms may include pain, atrophy, and tenderness around the distal or proximal patellar pole, or a history of Osgood–Schlatter disease or jumper's knee [36]. In the National Football League cohort, 11 of 24 players complained of anterior knee pain before rupture [57]. Of these patients, 10 had a diagnosis of patellar tendinosis and 1 had a diagnosis of patellofemoral pain [57].

Physical Examination

The key to diagnosing an extensor mechanism injury is the lack of active knee extension or the inability to maintain the passively extended knee against gravity [36]. The hallmark of patellar tendon injury is weakness or loss of active extension [54]. This deficit may be difficult to appreciate in the acutely painful and swollen knee, warranting a high index of suspicion [54]. Physical examination for a complete rupture demonstrates tenderness at the site of injury, hematoma, and a palpable defect in the tendon [28]. Patients with a complete rupture cannot extend the knee against resistance or perform a straight leg raise [28]. However, in incomplete ruptures or in patients with a complete quadriceps tendon rupture but an intact retinaculum, the ability to perform a straight leg raise against gravity may be uncompromised [28]. Most patellar tendon ruptures extend completely through the retinacular tissue, resulting in complete loss of knee extension [36]. Quadriceps tendon ruptures may not involve as much retinacular tissue, allowing some extension to remain possible [36]. Typically, some degree of extensor lag is almost always present when compared with the uninjured limb [36].

Palpation and Inspection

Immediately after injury, a defect may be palpable at the level of the rupture [36]. A palpable defect may also be observed if the tear is complete and the patella has migrated proximally [54]. Physical exam may show an acute hemarthrosis or a palpable defect at the level of the tendon [15]. When the diagnosis is delayed, the tendon defect may not be palpable secondary to consolidation of the hematoma and early scar formation [36]. The associated pain and disability is quite profound and could easily distract both the patient and clinician from other sites of injury [15].

Neglected Injuries

All patients with neglected patellar tendon ruptures demonstrated patella alta, quadriceps muscle atrophy, and weak or absent knee extension [20]. These patients had an extensor lag of greater than 20° with a maximum of 45° [20].

Imaging

Radiographs of the knee after patellar tendon rupture demonstrate patella alta, particularly with the knee flexed [28]. Lateral radiographs confirm the proximal position of the patella as compared with the uninjured side in cases of neglected patellar tendon rupture [20]. Radiographs obtained after quadriceps tendon rupture demonstrate patella baja and sometimes show bony fragments in the region of the rupture [28]. MRI can be helpful when the diagnosis is uncertain, particularly when differentiating between a partial and a complete rupture of a tendon [28].

Associated Injuries

There is a 30% incidence of intra-articular associated injuries in all patients with patellar tendon rupture [15]. ACL tears have accompanied up to 12.5% of high-level sporting injuries resulting in patellar tendon rupture and should be sought during the initial evaluation or with MRI [36]. In a study of patellar tendon ruptures, eight patients had either a medial tear, lateral tear, or both meniscuses torn (24%) [15].

Investigations

Physical Examination: History of symptoms occurring during knee flexion and careful physical examination of patella mobility are key diagnostic factors for distinguishing patellar dislocation from other pathologies [13]. In patients with extensor mechanism ruptures, physical examination may reveal an acute hemarthrosis or a palpable defect at the level of the tendon [15].

MRI: Magnetic resonance imaging can clearly delineate acute ruptures of the patellar ligament and avulsion fractures of the patella, aiding in diagnosis when radiographs are inconclusive due to small bone fragments [132]. MRI and ultrasound are reliable and interchangeable methods only for evaluating noninjured patellar tendons [136]. Partial-thickness tears are located posterior or posteromedially in the proximal patellar tendon, with tendon thickness >8.8 mm strongly correlated with the presence of a tear [47]. Preoperative MRI predicted the required quadriceps tendon length for ACL reconstruction, but 37% of patients lacked an adequate quadriceps tendon length [160]. The quadriceps tendon is significantly thicker than the patellar tendon at 1, 2, and 4 cm from the patella in both males and females based on preoperative MRI [66].

Other Considerations: A 30% incidence of intra-articular associated injuries was found in patients with patellar tendon rupture [15]. Eight patients with patellar tendon rupture had either a medial tear, lateral tear, or both meniscuses torn (24%) [15]. A quadriceps tendon shorter than 60 mm required the addition of patellar bone for ACL reconstruction [160]. The patellar tendon at the donor site healed gradually, as expressed by a decrease in the area of non-tendinous-like tissue signal on serial MRI evaluations [18]. Extensive calcification of the patellar tendon may form after removal of the central third for grafting, yet it can persist for more than eleven years without causing any complaint about range of motion or pain [24].

Treatment

Non-Operative

Nonsurgical treatment is indicated for partial rupture of the patellar or quadriceps tendon when no disruption of the extensor mechanism is present [28]. It is also indicated for patients who are unable to tolerate surgery because of poor overall medical condition [28]. Incomplete ruptures are usually managed conservatively without surgical intervention if full active extension is present on physical examination [115]. Nearly all patients with partial extensor mechanism tears underwent initial nonoperative management [150].

For patellar or quadriceps tendinopathy, initial treatment consists of activity modification [22]. Progressive flexibility and eccentric strengthening exercises follow initial activity modification [22]. Taping to aid proprioception and patellar tracking or using an infrapatellar strap can be helpful [22]. NSAIDs can be beneficial in the treatment of tendinopathy [22]. Corticosteroid injection is contraindicated in the treatment of tendinopathy because of the increased risk of tendon rupture [22]. No recommendation can be made currently regarding either prolotherapy injections using a local irritant to elicit an inflammatory healing response or platelet-rich plasma injection for tendinopathy [22].

Nonsurgical management of a complete quadriceps or patellar tendon rupture generally yields poor results with long-term disability in gait and weakness [115]. Untreated complete ruptures will result in ambulation with a stiff-knee gait or circumduction to allow the foot to clear the ground during the swing phase of gait [115]. Patients with untreated complete ruptures will complain of knee buckling and difficulty in climbing stairs [115]. The limb is initially immobilized with the knee in full extension for 4 to 6 weeks, after which, protected range of motion and strengthening are begun [115]. Initially, flexion of greater than 90 degrees is avoided to reduce stress on the tendon during nonoperative management [115]. Restrictions on flexion are removed once the patient achieves good quadriceps muscle control and is able to perform a straight-leg raise without discomfort [115].

Operative

Indications: Early surgery (within the first 2 weeks after injury) is recommended for complete rupture of the patellar or quadriceps tendon [28]. An early repair within 2 to 3 weeks of injury is the only factor that has been associated with better outcomes [44]. Patellar tendon rupture has a good prognosis if diagnosis and surgical treatment is early [14].

Surgical Approach / Technique: The patient is positioned supine on a standard operating table [19]. A small bump under the hip is often useful for controlling external rotation of the limb [19]. A small bump of towels that can be moved from beneath the knee and ankle and vice versa helps in providing slight knee flexion and extension, respectively, during the case [19]. A tourniquet is rarely needed; however, one may be placed in a nonsterile fashion and only inflated if uncontrollable bleeding is encountered [19]. Heavy nonabsorbable suture, a suture passer, and a drill are typically required for repair [19]. Inspection of the soft tissues for abrasions, lacerations, or prior incisions should occur prior to surgery and may influence the placement of the skin incision [19].

An anterior longitudinal midline incision is a key surgical step for acute extensor tendon rupture repair [19]. Expose tendon rupture is a key surgical step for acute extensor tendon rupture repair [19]. Remove nonviable tendon edges is a key surgical step for acute extensor tendon rupture repair [19]. Place grasping stitches in tendon is a key surgical step for acute extensor tendon rupture repair [19]. Reattach patellar or quadriceps tendon through three parallel longitudinal drill holes in the patella is a key surgical step for acute extensor tendon rupture repair [19]. Secure sutures over bone bridges in full extension is a key surgical step for acute extensor tendon rupture repair [19]. Assess strength of repair with controlled flexion is a key surgical step for acute extensor tendon rupture repair [19]. Consider adding a cerclage wire from quadriceps tendon to tibial tubercle for patellar tendon injury is a key surgical step for acute extensor tendon rupture repair [19]. Perform multilayer closure is a key surgical step for acute extensor tendon rupture repair [19].

For patellar tendon rupture repair, a midline incision is used [28]. Nonabsorbable sutures are placed in the tendon using a running locking stitch and passed through longitudinal drill holes in the patella [28]. The retinaculum is repaired with a heavy absorbable suture during patellar tendon rupture repair [28]. The paratenon is repaired if possible during patellar tendon rupture repair [28]. Ideally, the knee should flex to 90° after patellar tendon rupture repair [28].

For quadriceps tendon repair, a midline incision is used [28]. Longitudinal drill holes are placed in the patella, and the tendon is sutured using a heavy nonabsorbable suture in a running locking pattern for quadriceps tendon repair [28]. The retinaculum is sutured using a heavy absorbable suture during quadriceps tendon repair [28]. If necessary, reinforcement is performed using a quadriceps turndown, a pull-out wire, or a fascia lata or hamstrings autograft for quadriceps tendon repair [28]. Ideally, the knee should flex to 90° after quadriceps tendon repair [28].

The site of the tear (proximal, midsustance, or distal) will dictate the preferred surgical repair technique [102]. Most patellar tendon ruptures occur at the insertion on the inferior pole of the patella as an avulsion [102]. Avulsion of the patellar tendon from the inferior pole of the patella can be treated by debridement of the tendon, followed by the passage of two heavy nonabsorbable sutures into the tendon [102]. Three parallel drill holes are created from inferior to superior in the patella for avulsion repair [102]. The sutures are passed through the drill holes and tied at the superior pole of the patella for avulsion repair [102]. The medial and lateral retinacular tears are identified and repaired during avulsion repair [102]. A cerclage or reinforcement suture or wire is recommended for most cases of patellar tendon avulsion repair [102]. The cerclage wire or suture is performed by drilling a transverse tunnel 1 cm posterior to the tibial tubercle and passing heavy nonabsorbable suture or wire through the hole [102]. The wire or suture is brought proximally and passed under the quadriceps tendon close to the superior border of the patella and tensioned at 30 degrees of flexion [102]. The knee is flexed to 90 degrees to test the integrity of the repair after cerclage placement [102]. No complications and 100% good and excellent results were reported in 30 patients with patellar tendon avulsion repair employing a braided nonabsorbable suture [102]. The authors felt the braided nonabsorbable suture reinforced the repair and allowed early active motion and brace-free ambulation at 6 weeks [102].

Hamstring autograft can be utilized for patellar tendon avulsion repair [102]. The semitendinosus tendon is harvested with an open tendon stripper leaving the insertion intact for hamstring autograft repair [102]. The proximal aspect of the semitendinosus tendon is passed through a transverse drill hole in the patella and sutured to the distal lateral retinaculum or patellar tendon [102]. This method has been shown to lead to less gap formation at the repair in biomechanical studies [102]. The patellar tendon suture line is reinforced with absorbable sutures, the wound is closed in layers, and a well-padded dressing is applied [102]. A hinged knee brace is applied with the knee in full extension after patellar tendon avulsion repair [102].

A midsustance tear is more difficult to repair as the quality of tissue may be compromised and caution should be observed to prevent shortening of the tendon and creating patella baja with placement of the sutures [102]. The most common method of repair for midsustance tears involves simple end-to-end repair, with or without a reinforcing cerclage suture of wire or nonabsorbable suture material or tape [102]. A distal patellar tendon rupture from the tibial tubercle is the least common pattern [102]. A suture repair through bone tunnels with semitendinosus and gracilis augmentation as described for late reconstruction is recommended for distal patellar tendon ruptures [102].

Three parallel drill holes are created from superior to inferior through the patella for quadriceps avulsion repair [19]. The sutures are passed through the drill holes and tied at the inferior patella and the retinacular tissue is repaired [19].

Make a midline longitudinal incision 15 to 20 cm long to expose the rupture for quadriceps tendon repair [58]. Irrigate the hematoma and freshen the tendon ends for quadriceps tendon repair [58]. If sufficient tendon is left distally, make an end-to-end repair using multiple No. 2 or No. 5 nonabsorbable mattress sutures through the tendon and No. 0 absorbable sutures to repair the retinaculum [58]. Carefully align the tendon and evaluate patellar tracking and position [58]. Use a circumferential wire or suture for protection of the repair [58]. In ruptures at the osteotendinous junction, an 8- to 10-mm stump of vastus intermedius often is left attached to the patella [58]. Place No. 0 nonabsorbable sutures through the stump and lay them aside for later use [58]. With a rongeur, make a small trough in the superior pole of the patella [58]. Drill three longitudinal holes about 1 cm apart centered over the anticipated area of attachment of the quadriceps tendon [58]. Pass a No. 5 nonabsorbable suture proximally through the quadriceps tendon, using a running interlocking suture, for a distance of about 2.5 cm, until normal-appearing tendon is reached [58]. Pass the suture distally in a similar manner, ending just lateral to the midline of the ruptured tendon [58]. Pass similar sutures along the medial side of the tendon and distally as previously described [58]. Pass the suture distally with a suture retriever or Beath pin, place a single throw in the suture, and secure it with a hemostat [58]. Move the knee through a range of motion to check patellar tracking and position [58]. If placement is satisfactory, bring the sutures in the vastus intermedius stump anteriorly and secure them through the quadriceps tendon while maintaining anatomic position [58]. Tie the sutures distally, drawing the tendon into the bony trough [58]. Repair the retinaculum with interrupted absorbable sutures and close the skin and subcutaneous tissue in a routine manner [58]. Apply a cylinder cast or locked brace with the knee in extension [58]. The cylinder cast or locked brace is worn for 6 weeks postoperatively [58]. Weight bearing with crutches is allowed at 3 weeks postoperatively [58]. Cast removal and a dial-locked brace is fitted, allowing a range of knee motion from 0

Other Considerations: Most series have reported between 70% and 100% good to excellent results for acute patellar tendon repair [44]. The majority of patients who undergo early primary repair achieve a functional range of motion and normal quadriceps strength [44]. Persistent quadriceps muscle atrophy commonly occurs after early primary repair but has not been correlated with loss of strength [44]. No relationship has been demonstrated between the configuration of the rupture, the method of repair, and clinical outcome [44]. Siwek and Rao reviewed 25 patients treated within 7 days and found that 96% had good to excellent results [44]. Only two of the six patients with a delayed repair in the Siwek and Rao review had excellent results [44]. A greater degree of persistent quadriceps atrophy was noted in patients treated with delayed repair in the Siwek and Rao review [44]. Hsu et al. reported 20 excellent (57%) and 10 (29%) good results in 35 traumatic patellar tendon ruptures treated acutely with primary repair and a neutralization wire [44]. West et al. demonstrated no complications and excellent results in 30 patellar tendon ruptures treated with transosseous sutures and a braided nonabsorbable relaxing suture placed through the quadriceps tendon and retinaculum and around the distal patella tensioned at 30 degrees of flexion [44]. West et al. instituted range of motion from 0 to 55 degrees at 7 days and weaned the patient to brace-free ambulation at 6 weeks [44].

Surgical procedures for tendinopathy include various methods of débriding diseased tissue and stimulating a vigorous healing response [22]. Débridement of diseased tissue can be achieved by simple longitudinal excision of the diseased portion of tendon, followed by abrasion of the bone to provide a bleeding surface for tendon healing [22]. Débridement for tendinopathy can be finished with the application of side-to-side sutures or suture anchors as needed [22]. Variations of débridement for tendinopathy include drilling of the bone to stimulate a healing response or multiple tendon perforations (“pie crusting”) to stimulate healing of the tendon tissue [22]. All surgical procedures for tendinopathy can be performed using a standard anterior midline incision to expose the diseased tendon and its attachment to the patella [22]. Arthroscopic patellar release translates into sustained pain relief and functional improvement over a long-term follow-up in athletes with chronic symptomatic patellar tendinopathy [69].

Complications

Associated Injuries

No specific evidence regarding associated injuries is provided in the current dataset.

Chronic and Neglected Ruptures

Missed diagnoses and delayed treatment of quadriceps and patellar tendon tears lead to challenging reconstructions with less predictable results [2]. Chronic or neglected patellar tendon ruptures present significant operative challenges due to the unopposed pull of the quadriceps muscles, which can result in significant contraction of the extensor mechanism [44]. Consequently, results for reconstruction of chronic patellar tendon rupture have generally been less satisfactory compared to acute repair [44]. Primary repair has very poor results in the management of chronic complete patellar tendon disruptions [30].

Operative repair of chronic patellar tendon rupture can be complicated by proximal retraction of the patella and by insufficient tissue for repair [28]. Chronic quadriceps tendon ruptures can be complicated by proximal migration of the tendon stump, which requires débridement and mobilization of the tendon [28]. In a series of four patients with neglected patellar tendon ruptures (injuries more than 6 months old), all demonstrated patella alta, quadriceps muscle atrophy, and weak or absent knee extension [20]. These patients also had an extensor lag of greater than 20° with a maximum of 45° [20].

Post-Operative Outcomes and Complications

Persistent quadriceps muscle atrophy commonly occurs after early primary repair of patellar tendon rupture, but has not been correlated with loss of strength [44]. No relationship has been demonstrated between the configuration of the rupture, the method of repair, and clinical outcome for acute patellar tendon rupture [44]. Seven of 10 patients who underwent operative repair of acute patellar tendon ruptures demonstrated incongruity on Merchant and lateral radiographs [44]. Patients with residual patellofemoral symptoms after acute patellar tendon repair all had incongruity, but the majority were asymptomatic [44]. Articular incongruity may not be the only cause of persistent knee pain in patients who undergo patellar tendon repair [44].

The possibility of rupture of a patellar ligament allograft in the future must be considered because one would not expect that a patellar ligament allograft would be vascularized fully after two years [26]. The contralateral bone–patellar tendon graft presents no advantage over the ipsilateral graft, as all symptoms concerning donor site morbidity are shifted from the injured into the healthy knee, and return to activity is not more rapid [68].

Total Knee Arthroplasty Context

Patellar tendon ruptures account for less than 1% of complications occurring after total knee arthroplasty [30]. Reconstruction of patellar tendon rupture has a much lower complication rate than repair, supporting the recommendation of patellar tendon reconstruction in both early and late presentation stages after total knee arthroplasty [3]. The medial gastrocnemius transposition flap may be best suited for the treatment of complicated disruptions of the extensor mechanism in patients who have had a failed repair of the quadriceps or who have a rupture of the patellar ligament and poor soft-tissue coverage, poor healing potential, inadequate patellar bone stock, or an exposed prosthesis with loss of the extensor mechanism [5].

Recovery

Acute Repair Outcomes: Surgical treatment of both quadriceps and patellar tendon ruptures yields good to excellent outcomes [1]. For acute patellar tendon ruptures, early repair within 2 to 3 weeks of injury is the only factor associated with better outcomes [44]. In a review of 25 patients treated within 7 days, 96% achieved good to excellent results, whereas only two of six patients undergoing delayed repair achieved excellent results [44]. Patients treated with delayed repair demonstrated a greater degree of persistent quadriceps atrophy compared to those treated early [44]. Although persistent quadriceps muscle atrophy commonly occurs after acute patellar tendon repair, it has not been correlated with loss of strength [44]. No relationship has been demonstrated between the configuration of the rupture, the method of repair, and clinical outcome for acute patellar tendon ruptures [44]. Acute surgical repair of quadriceps tendon ruptures provides better knee function compared to the surgical restoration of patellar tendon rupture [7].

Rehabilitation Protocol: In a series of 30 patellar tendon ruptures treated with transosseous sutures and a braided nonabsorbable relaxing suture, range of motion from 0 to 55 degrees was instituted at 7 days, and patients were weaned to brace-free ambulation at 6 weeks [44]. This protocol demonstrated no complications and excellent results [44].

Chronic or Neglected Rupture Outcomes: Hamstring tendon reconstruction of chronic patellar tendon rupture provides good functional recovery and return to preinjury daily activities [27]. The use of hamstring tendons is a good option for the management of chronic quadriceps tendon tears, providing good results despite a 7-month delay between injury and surgery [46].

Other Considerations: The possibility of rupture of a patellar ligament allograft in the future must be considered because a patellar ligament allograft would not be expected to be vascularized fully after two years [26].

Key Evidence

  • [L3] Good to excellent outcomes were revealed in both quadriceps and patellar tendon rupture groups. [1] (10.1016/j.injury.2015.06.042)
  • [L5] Adequate repair of the quadriceps and patellar tendons is essential for a functional extensor mechanism; missed diagnoses and delayed treatment lead to challenging reconstructions with less predictable results. [2] (10.1007/s11999-013-3396-6)
  • [L4] Reconstruction of patellar tendon rupture has a much lower complication rate than repair, supporting the recommendation of patellar tendon reconstruction in both early and late presentation stages. [3] (10.1016/j.arth.2019.02.046)
  • [L4] Good functional and objective results can be obtained in patellar tendon ruptures repaired early using only a sturdy primary repair that allows early, controlled motion of the knee. [4] (10.1177/03635465990270030601)
  • [L4] It may be best suited for the treatment of complicated disruptions of the extensor mechanism in patients who have had a failed repair of the quadriceps or who have a rupture of the patellar ligament and poor soft-tissue coverage, poor healing potential, inadequate patellar bone stock, or an exposed prosthesis with loss of the extensor mechanism. [5] (10.2106/00004623-199706000-00010)
  • [L4] Early surgical management is generally needed for quadriceps and patellar tendon tears to restore function, with specific techniques varying based on the lesion type and chronicity. [6] (10.1016/j.otsr.2012.12.002)
  • [L3] Acute surgical repair of quadriceps tendon ruptures provides better knee function, in comparison to the surgical restoration of patellar tendon rupture. [7] (10.1016/j.otsr.2018.09.019)
  • [Case_report] Immediate primary repair of the patellar tendon and delayed reconstruction of the ACL is the preferred treatment option. [8] (10.1007/s00167-006-0048-3)
  • [L4] Quadriceps and patellar tendon repairs protected by a relaxing suture were strong enough to safely permit early motion, weightbearing, and brace-free ambulation while producing good and excellent results. [11] (10.1177/0363546507308192)
  • [L4] History of symptoms occurring in knee flexion and careful physical examination of patella mobility are key diagnostic factors. [13] (10.1007/s00167-013-2729-z)
  • [L4] Patellar tendon rupture has a good prognosis if diagnosis and surgical treatment is early. [14] (10.1016/j.otsr.2014.12.017)
  • [L4] [15] (10.1007/s00167-008-0516-z)
  • [L4] Patellar tendon ruptures are rare after ACL graft harvest and typically occur in a proximal-medial/distal-lateral or entirely distal pattern. [17] (10.1177/0363546512449815)
  • [L2] The patellar tendon at the donor site healed gradually, as expressed by a decrease in the area of non-tendinous-like tissue signal on serial MRI evaluations. [18] (10.1007/s001670050115)
  • [L4] [20] (10.1177/03635465010290041301)
  • [L4] In the setting of MLKI, patients who have a concomitant patellar tendon rupture have worse functional outcomes compared to those without. [21] (10.1007/s00167-022-07110-3)
  • [L4] Extensive calcification of the patellar tendon may form after removal of the central third for grafting, yet it can persist for more than eleven years without causing any complaint about range of motion or pain. [24] (10.1007/s00167-003-0424-1)
  • [Case_report] The possibility of rupture of such a graft in the future must be considered because one would not expect that a patellar ligament allograft would be vascularized fully after two years. [26] (10.2106/00004623-199407000-00019)
  • [L4] Hamstring tendon reconstruction of chronic patellar tendon rupture provided good functional recovery and return to preinjury daily activities. [27] (10.2106/jbjs.l.01462)
  • [L4] Patellar tendon rupture is rare in the pediatric population and represents 7% of pediatric patients who sustained acute traumatic injury of the knee extensor mechanism. [29] (10.1016/j.injury.2017.08.069)
  • [L4] [30] (10.1007/s00167-014-3189-9)
  • [L4] Surgical reconstruction of chronic patellar tendon ruptures using contralateral bone-tendon-bone graft was a safe and viable option that improves clinical and functional outcomes compared to presurgical function. [31] (10.1007/s00167-015-3951-7)
  • [L3] The shortening of the patellar tendon correlates with the severity of the patellofemoral osteoarthritis. [32] (10.1177/03635465010290010701)
  • [L4] The use of hamstring tendons is a good option for the management of chronic quadriceps tendon tears, providing good results despite a 7-month delay between injury and surgery. [46] (10.1007/s00167-006-0044-7)
  • [L2] Partial-thickness tears are located posterior or posteromedially in the proximal patellar tendon, with tendon thickness >8.8 mm strongly correlated with the presence of a tear. [47] (10.1177/0363546519894333)
  • [L3] Patients with complications after anterior cruciate ligament reconstruction with a patellar tendon autograft may have less difficulty obtaining full knee motion when the graft is harvested from the contralateral knee. [48] (10.1177/0363546510388163)
  • [L5] [53] (10.5435/jaaosglobal-d-24-00060)
  • [L4] [54] (10.1530/eor-22-0021)
  • [L4] [57] (10.1177/0363546511417083)
  • [L4] The hamstring tendon autograft is a safe, effective, and acceptable choice for patellar tendon reconstruction. [60] (10.1007/s00402-014-2080-y)
  • [L4] Suture anchor fixation of the quadriceps tendon is a viable option in the setting of rupture after total knee arthroplasty, offering advantages such as less soft tissue dissection and avoidance of violation of the patella tendon. [65] (10.1016/j.arth.2011.01.006)
  • [L4] The quadriceps tendon is significantly thicker than the patellar tendon at 1, 2, and 4 cm from the patella in both males and females based on preoperative MRI before ACL surgery. [66] (10.1016/j.asmr.2023.04.005)
  • [L4] The use of fresh-frozen allografts as a solution to patellar tendon ruptures after knee arthroplasty seems to provide acceptable results. [67] (10.1007/s00167-013-2688-4)
  • [L2] The contralateral bone–patellar tendon graft appears to present no advantage over the ipsilateral graft, as all symptoms concerning donor site morbidity are shifted from the injured into the healthy knee, and return to activity is not more rapid. [68] (10.1177/0363546504265926)
  • [L4] Arthroscopic patellar release translates into sustained pain relief and functional improvement over a long-term follow-up in athletes. [69] (10.1186/s12891-017-1851-3)
  • [L3] Patients should be counseled regarding a high reoperation and infection rate, and direct repair of patellar tendon injuries should likely be avoided due to a rate of poor outcomes of 63%. [71] (10.1016/j.arth.2017.11.045)
  • [L4] The altered function of the patellar tendon in anterior cruciate ligament deficiency resulted in an altered patellar tracking and patellofemoral cartilage contact. [113] (10.1177/0363546508314404)
  • [L5] The central third of a non-irradiated, human bone–patellar tendon–bone construct is thicker and biomechanically superior to the medial and lateral regions in most respects. [114] (10.1007/s00167-013-2768-5)
  • [L4] [124] (10.1016/j.otsr.2011.01.015)
  • [L5] Based on mechanical tensile properties analyses, the quadriceps tendon-bone construct may represent a versatile alternative graft in primary and revision anterior and posterior cruciate ligament reconstruction. [131] (10.1177/03635465990270011301)
  • [Case_report] Magnetic resonance imaging can clearly delineate acute ruptures of the patellar ligament and avulsion fractures of the patella, aiding in diagnosis when radiographs are inconclusive due to small bone fragments. [132] (10.2106/00004623-199511000-00012)
  • [L5] Concurrent increases in patellar tendon and ACL strains indicate that the quadriceps load the ACL via the patella tendon when the knee is positioned near extension. [134] (10.1177/2325967121991054)
  • [L3] MRI and US are reliable (interchangeable) methods only for evaluating noninjured patellar tendons. [136] (10.1007/s001670000132)
  • [L5] Nearly all patients with partial extensor mechanism tears underwent initial nonoperative management. [150] (10.1016/j.asmr.2024.100944)
  • [L3] [154] (10.1177/0363546515576902)
  • [L3] Although preoperative MRI predicted the required QT length for ACL reconstruction, 37% of patients lacked an adequate QT length, and a QT shorter than 60 mm required the addition of patellar bone. [160] (10.1007/s00167-020-06261-5)

See Also

References

[1] Extensor mechanism ruptures of the knee: Differences in demographic data and long-term outcome after surgical treatment. Injury. 2015. DOI: 10.1016/j.injury.2015.06.042

[2] Complications in Brief: Quadriceps and Patellar Tendon Tears. Clinical Orthopaedics & Related Research. 2014. DOI: 10.1007/s11999-013-3396-6

[3] Treatment of Extensor Tendon Disruption After Total Knee Arthroplasty: A Systematic Review. The Journal of Arthroplasty. 2019. DOI: 10.1016/j.arth.2019.02.046

[4] Primary Repair of Patellar Tendon Rupture Without Augmentation. The American Journal of Sports Medicine. 1999. DOI: 10.1177/03635465990270030601

[5] Medial Gastrocnemius Transposition Flap for the Treatment of Disruption of the Extensor Mechanism after Total Knee Arthroplasty. The Journal of Bone & Joint Surgery*. 1997. DOI: 10.2106/00004623-199706000-00010

[6] Acute and old ruptures of the extensor apparatus of the knee in adults (excluding knee replacement). Orthopaedics & Traumatology: Surgery & Research. 2013. DOI: 10.1016/j.otsr.2012.12.002

[7] Better knee function after surgical repair of acute quadriceps tendon rupture in comparison to acute patellar tendon rupture. Orthopaedics & Traumatology: Surgery & Research. 2019. DOI: 10.1016/j.otsr.2018.09.019

[8] Simultaneous rupture of the patellar tendon and the anterior cruciate ligament: a case report and literature review. Knee Surgery, Sports Traumatology, Arthroscopy. 2006. DOI: 10.1007/s00167-006-0048-3

[11] Early Motion after Quadriceps and Patellar Tendon Repairs. The American Journal of Sports Medicine. 2007. DOI: 10.1177/0363546507308192

[13] Displacing lateral meniscus masquerading as patella dislocation. Knee Surgery, Sports Traumatology, Arthroscopy. 2013. DOI: 10.1007/s00167-013-2729-z

[14] Acute traumatic patellar tendon rupture: Early and late results of surgical treatment of 38 cases. Orthopaedics & Traumatology: Surgery & Research. 2015. DOI: 10.1016/j.otsr.2014.12.017

[15] Intra‐articular knee injuries in patients with knee extensor mechanism ruptures. Knee Surgery, Sports Traumatology, Arthroscopy. 2008. DOI: 10.1007/s00167-008-0516-z

[17] Tear Patterns, Surgical Repair, and Clinical Outcomes of Patellar Tendon Ruptures After Anterior Cruciate Ligament Reconstruction With a Bone–Patellar Tendon–Bone Autograft. The American Journal of Sports Medicine. 2012. DOI: 10.1177/0363546512449815

[18] Serial magnetic resonance imaging of the donor site after harvesting the central third of the patellar tendon. Knee Surgery, Sports Traumatology, Arthroscopy. 1999. DOI: 10.1007/s001670050115

[19] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Operative Treatment of Extensor Mechanism Injuries.

[20] Neglected Ruptures of the Patellar Tendon. The American Journal of Sports Medicine. 2001. DOI: 10.1177/03635465010290041301

[21] Poorer functional Outcomes in Patients with Multi‐Ligamentous Knee Injury with Concomitant Patellar Tendon Ruptures at 5 years Follow‐Up. Knee Surgery, Sports Traumatology, Arthroscopy. 2022. DOI: 10.1007/s00167-022-07110-3

[22] Aaos Comprehensive Orthopaedic Review 3. Extensor Mechanism Injuries > IV Patellar or Quadriceps Tendinopathy.

[24] Calcification of the patellar tendon after ACL reconstruction. Knee Surgery, Sports Traumatology, Arthroscopy. 2004. DOI: 10.1007/s00167-003-0424-1

[26] Allograft reconstruction of the patellar ligament. A case report.. The Journal of Bone & Joint Surgery. 1994. DOI: 10.2106/00004623-199407000-00019

[27] Ipsilateral Hamstring Tendon Graft Reconstruction for Chronic Patellar Tendon Ruptures. Journal of Bone and Joint Surgery. 2013. DOI: 10.2106/jbjs.l.01462

[28] Aaos Comprehensive Orthopaedic Review 3. Extensor Mechanism Injuries > III Rupture of the Patellar Tendon or Quadriceps Tendon.

[29] Acute traumatic rupture of the patellar tendon in pediatric population: Case series and review of the literature. Injury. 2017. DOI: 10.1016/j.injury.2017.08.069

[30] Complications involving the extensor mechanism after total knee arthroplasty. Knee Surgery, Sports Traumatology, Arthroscopy. 2014. DOI: 10.1007/s00167-014-3189-9

[31] Reconstruction of chronic patellar tendon rupture with contralateral bone-tendon-bone autograft. Knee Surgery, Sports Traumatology, Arthroscopy. 2015. DOI: 10.1007/s00167-015-3951-7

[32] The Incidence of Patellofemoral Osteoarthritis and Associated Findings 7 Years after Anterior Cruciate Ligament Reconstruction with a Bone-Patellar Tendon-Bone Autograft. The American Journal of Sports Medicine. 2001. DOI: 10.1177/03635465010290010701

[36] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Extensor Mechanism Injuries.

[44] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Chronic or Neglected Quadriceps and Patellar Tendon Ruptures > Acute Patellar Tendon Repair.

[46] Reconstruction of a chronic quadriceps tendon tear in a body builder. Knee Surgery, Sports Traumatology, Arthroscopy. 2006. DOI: 10.1007/s00167-006-0044-7

[47] Rethinking Patellar Tendinopathy and Partial Patellar Tendon Tears: A Novel Classification System. The American Journal of Sports Medicine. 2020. DOI: 10.1177/0363546519894333

[48] Infections and Patellar Tendon Ruptures After Anterior Cruciate Ligament Reconstruction. The American Journal of Sports Medicine. 2011. DOI: 10.1177/0363546510388163

[53] Acute Patellar Tendon Ruptures: An Update on Management. JAAOS: Global Research and Reviews. 2024. DOI: 10.5435/jaaosglobal-d-24-00060

[54] Extensor mechanism ruptures. EFORT Open Reviews. 2022. DOI: 10.1530/eor-22-0021

[57] Patellar Tendon Ruptures in National Football League Players. The American Journal of Sports Medicine. 2011. DOI: 10.1177/0363546511417083

[58] Campbell S Operative Orthopaedics 4 Volume Set. SUTURE ANCHOR REPAIR OF PATELLAR TENDON RUPTURE > REPAIR OF ACUTE RUPTURE OF THE TENDON OF THE QUADRICEPS FEMORIS MUSCLE > TECHNIQUE 48.27.

[60] Reconstruction of a chronic patellar tendon rupture with semitendinosus autograft. Archives of Orthopaedic and Trauma Surgery. 2014. DOI: 10.1007/s00402-014-2080-y

[62] Orthopaedic Knowledge Update 13 Ebook Without Multimedia. Soft-­Tissue Injuries About the Knee > Patellar Tendon > Patellar Tendon Rupture.

[65] Suture Anchor Repair of Quadriceps Tendon Rupture After Total Knee Arthroplasty. The Journal of Arthroplasty. 2011. DOI: 10.1016/j.arth.2011.01.006

[66] Two‐Dimensional Magnetic Resonance Imaging in Preparation for Autograft Anterior Cruciate Ligament Reconstruction Demonstrates Quadriceps Tendon Is Thicker Than Patellar Tendon. Arthroscopy, Sports Medicine, and Rehabilitation. 2023. DOI: 10.1016/j.asmr.2023.04.005

[67] Reconstruction of the extensor mechanism with fresh‐frozen tendon allograft in total knee arthroplasty. Knee Surgery, Sports Traumatology, Arthroscopy. 2013. DOI: 10.1007/s00167-013-2688-4

[68] Donor Site Morbidity and Return to the Preinjury Activity Level after Anterior Cruciate Ligament Reconstruction Using Ipsilateral and Contralateral Patellar Tendon Autograft. The American Journal of Sports Medicine. 2005. DOI: 10.1177/0363546504265926

[69] Arthroscopic patellar release for treatment of chronic symptomatic patellar tendinopathy: long-term outcome and influential factors in an athletic population. BMC Musculoskeletal Disorders. 2017. DOI: 10.1186/s12891-017-1851-3

[71] Is There Any Role for Direct Repair of Extensor Mechanism Disruption Following Total Knee Arthroplasty?. The Journal of Arthroplasty. 2018. DOI: 10.1016/j.arth.2017.11.045

[96] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Pathoanatomy and Applied Anatomy Related to Extensor Mechanism Injuries.

[102] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Acute Patellar Tendon Rupture.

[110] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Assessment of Patellar Fractures.

[111] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Soft Tissue Anatomy.

[113] The Effect of Anterior Cruciate Ligament Deficiency and Reconstruction on the Patellofemoral Joint. The American Journal of Sports Medicine. 2008. DOI: 10.1177/0363546508314404

[114] Regional mechanical properties of human patellar tendon allografts. Knee Surgery, Sports Traumatology, Arthroscopy. 2013. DOI: 10.1007/s00167-013-2768-5

[115] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Nonoperative Treatment of Extensor Mechanism Rupture.

[124] Chronic patellar tendon rupture reconstruction with a semitendinosus autograft. Orthopaedics & Traumatology: Surgery & Research. 2011. DOI: 10.1016/j.otsr.2011.01.015

[131] Mechanical Tensile Properties of the Quadriceps Tendon and Patellar Ligament in Young Adults. The American Journal of Sports Medicine. 1999. DOI: 10.1177/03635465990270011301

[132] Demonstration of avulsion fracture of the inferior pole of the patella by magnetic resonance imaging. A case report.. The Journal of Bone & Joint Surgery. 1995. DOI: 10.2106/00004623-199511000-00012

[134] Patellar Tendon Orientation and Strain Are Predictors of ACL Strain In Vivo During a Single-Leg Jump. Orthopaedic Journal of Sports Medicine. 2021. DOI: 10.1177/2325967121991054

[136] Evaluation of harvested and normal patellar tendons: a reliability analyses of magnetic resonance imaging and ultrasonography. Knee Surgery, Sports Traumatology, Arthroscopy. 2000. DOI: 10.1007/s001670000132

[150] Athletes With Partial Extensor Mechanism Tears of the Knee Achieve Variable Return‐to‐Sport Rates Following Operative Versus Nonoperative Management: A Systematic Review. Arthroscopy, Sports Medicine, and Rehabilitation. 2024. DOI: 10.1016/j.asmr.2024.100944

[154] Medial Patellofemoral Ligament Tears in the Setting of Multiligament Knee Injuries Rarely Cause Patellar Instability. The American Journal of Sports Medicine. 2015. DOI: 10.1177/0363546515576902

[160] Patients with a quadriceps tendon shorter than 60 mm require a patellar bone plug autograft in anterior cruciate ligament reconstruction. Knee Surgery, Sports Traumatology, Arthroscopy. 2020. DOI: 10.1007/s00167-020-06261-5

Creative Commons BY-NC 4.0

CC Creative Commons licence
BY Attribution — you must credit the source
NC NonCommercial — not for commercial use

Attribution-NonCommercial 4.0 International

Creative Commons Corporation ("Creative Commons") is not a law firm and does not provide legal services or legal advice. Distribution of Creative Commons public licenses does not create a lawyer-client or other relationship. Creative Commons makes its licenses and related information available on an "as-is" basis. Creative Commons gives no warranties regarding its licenses, any material licensed under their terms and conditions, or any related information. Creative Commons disclaims all liability for damages resulting from their use to the fullest extent possible.

Using Creative Commons Public Licenses

Creative Commons public licenses provide a standard set of terms and conditions that creators and other rights holders may use to share original works of authorship and other material subject to copyright and certain other rights specified in the public license below. The following considerations are for informational purposes only, are not exhaustive, and do not form part of our licenses.

Considerations for licensors: Our public licenses are intended for use by those authorized to give the public permission to use material in ways otherwise restricted by copyright and certain other rights. Our licenses are irrevocable. Licensors should read and understand the terms and conditions of the license they choose before applying it. Licensors should also secure all rights necessary before applying our licenses so that the public can reuse the material as expected. Licensors should clearly mark any material not subject to the license. This includes other CC- licensed material, or material used under an exception or limitation to copyright. More considerations for licensors: wiki.creativecommons.org/Considerations_for_licensors

Considerations for the public: By using one of our public licenses, a licensor grants the public permission to use the licensed material under specified terms and conditions. If the licensor's permission is not necessary for any reason--for example, because of any applicable exception or limitation to copyright--then that use is not regulated by the license. Our licenses grant only permissions under copyright and certain other rights that a licensor has authority to grant. Use of the licensed material may still be restricted for other reasons, including because others have copyright or other rights in the material. A licensor may make special requests, such as asking that all changes be marked or described. Although not required by our licenses, you are encouraged to respect those requests where reasonable. More considerations for the public: wiki.creativecommons.org/Considerations_for_licensees

Creative Commons Attribution-NonCommercial 4.0 International Public License

By exercising the Licensed Rights (defined below), You accept and agree to be bound by the terms and conditions of this Creative Commons Attribution-NonCommercial 4.0 International Public License ("Public License"). To the extent this Public License may be interpreted as a contract, You are granted the Licensed Rights in consideration of Your acceptance of these terms and conditions, and the Licensor grants You such rights in consideration of benefits the Licensor receives from making the Licensed Material available under these terms and conditions.

Section 1 -- Definitions.

a. Adapted Material means material subject to Copyright and Similar Rights that is derived from or based upon the Licensed Material and in which the Licensed Material is translated, altered, arranged, transformed, or otherwise modified in a manner requiring permission under the Copyright and Similar Rights held by the Licensor. For purposes of this Public License, where the Licensed Material is a musical work, performance, or sound recording, Adapted Material is always produced where the Licensed Material is synched in timed relation with a moving image.

b. Adapter's License means the license You apply to Your Copyright and Similar Rights in Your contributions to Adapted Material in accordance with the terms and conditions of this Public License.

c. Copyright and Similar Rights means copyright and/or similar rights closely related to copyright including, without limitation, performance, broadcast, sound recording, and Sui Generis Database Rights, without regard to how the rights are labeled or categorized. For purposes of this Public License, the rights specified in Section 2(b)(1)-(2) are not Copyright and Similar Rights.

d. Effective Technological Measures means those measures that, in the absence of proper authority, may not be circumvented under laws fulfilling obligations under Article 11 of the WIPO Copyright Treaty adopted on December 20, 1996, and/or similar international agreements.

e. Exceptions and Limitations means fair use, fair dealing, and/or any other exception or limitation to Copyright and Similar Rights that applies to Your use of the Licensed Material.

f. Licensed Material means the artistic or literary work, database, or other material to which the Licensor applied this Public License.

g. Licensed Rights means the rights granted to You subject to the terms and conditions of this Public License, which are limited to all Copyright and Similar Rights that apply to Your use of the Licensed Material and that the Licensor has authority to license.

h. Licensor means the individual(s) or entity(ies) granting rights under this Public License.

i. NonCommercial means not primarily intended for or directed towards commercial advantage or monetary compensation. For purposes of this Public License, the exchange of the Licensed Material for other material subject to Copyright and Similar Rights by digital file-sharing or similar means is NonCommercial provided there is no payment of monetary compensation in connection with the exchange.

j. Share means to provide material to the public by any means or process that requires permission under the Licensed Rights, such as reproduction, public display, public performance, distribution, dissemination, communication, or importation, and to make material available to the public including in ways that members of the public may access the material from a place and at a time individually chosen by them.

k. Sui Generis Database Rights means rights other than copyright resulting from Directive 96/9/EC of the European Parliament and of the Council of 11 March 1996 on the legal protection of databases, as amended and/or succeeded, as well as other essentially equivalent rights anywhere in the world.

l. You means the individual or entity exercising the Licensed Rights under this Public License. Your has a corresponding meaning.

Section 2 -- Scope.

a. License grant.

1. Subject to the terms and conditions of this Public License, the Licensor hereby grants You a worldwide, royalty-free, non-sublicensable, non-exclusive, irrevocable license to exercise the Licensed Rights in the Licensed Material to:

a. reproduce and Share the Licensed Material, in whole or in part, for NonCommercial purposes only; and

b. produce, reproduce, and Share Adapted Material for NonCommercial purposes only.

2. Exceptions and Limitations. For the avoidance of doubt, where Exceptions and Limitations apply to Your use, this Public License does not apply, and You do not need to comply with its terms and conditions.

3. Term. The term of this Public License is specified in Section 6(a).

4. Media and formats; technical modifications allowed. The Licensor authorizes You to exercise the Licensed Rights in all media and formats whether now known or hereafter created, and to make technical modifications necessary to do so. The Licensor waives and/or agrees not to assert any right or authority to forbid You from making technical modifications necessary to exercise the Licensed Rights, including technical modifications necessary to circumvent Effective Technological Measures. For purposes of this Public License, simply making modifications authorized by this Section 2(a) (4) never produces Adapted Material.

5. Downstream recipients.

a. Offer from the Licensor -- Licensed Material. Every recipient of the Licensed Material automatically receives an offer from the Licensor to exercise the Licensed Rights under the terms and conditions of this Public License.

b. No downstream restrictions. You may not offer or impose any additional or different terms or conditions on, or apply any Effective Technological Measures to, the Licensed Material if doing so restricts exercise of the Licensed Rights by any recipient of the Licensed Material.

6. No endorsement. Nothing in this Public License constitutes or may be construed as permission to assert or imply that You are, or that Your use of the Licensed Material is, connected with, or sponsored, endorsed, or granted official status by, the Licensor or others designated to receive attribution as provided in Section 3(a)(1)(A)(i).

b. Other rights.

1. Moral rights, such as the right of integrity, are not licensed under this Public License, nor are publicity, privacy, and/or other similar personality rights; however, to the extent possible, the Licensor waives and/or agrees not to assert any such rights held by the Licensor to the limited extent necessary to allow You to exercise the Licensed Rights, but not otherwise.

2. Patent and trademark rights are not licensed under this Public License.

3. To the extent possible, the Licensor waives any right to collect royalties from You for the exercise of the Licensed Rights, whether directly or through a collecting society under any voluntary or waivable statutory or compulsory licensing scheme. In all other cases the Licensor expressly reserves any right to collect such royalties, including when the Licensed Material is used other than for NonCommercial purposes.

Section 3 -- License Conditions.

Your exercise of the Licensed Rights is expressly made subject to the following conditions.

a. Attribution.

1. If You Share the Licensed Material (including in modified form), You must:

a. retain the following if it is supplied by the Licensor with the Licensed Material:

i. identification of the creator(s) of the Licensed Material and any others designated to receive attribution, in any reasonable manner requested by the Licensor (including by pseudonym if designated);

ii. a copyright notice;

iii. a notice that refers to this Public License;

iv. a notice that refers to the disclaimer of warranties;

v. a URI or hyperlink to the Licensed Material to the extent reasonably practicable;

b. indicate if You modified the Licensed Material and retain an indication of any previous modifications; and

c. indicate the Licensed Material is licensed under this Public License, and include the text of, or the URI or hyperlink to, this Public License.

2. You may satisfy the conditions in Section 3(a)(1) in any reasonable manner based on the medium, means, and context in which You Share the Licensed Material. For example, it may be reasonable to satisfy the conditions by providing a URI or hyperlink to a resource that includes the required information.

3. If requested by the Licensor, You must remove any of the information required by Section 3(a)(1)(A) to the extent reasonably practicable.

4. If You Share Adapted Material You produce, the Adapter's License You apply must not prevent recipients of the Adapted Material from complying with this Public License.

Section 4 -- Sui Generis Database Rights.

Where the Licensed Rights include Sui Generis Database Rights that apply to Your use of the Licensed Material:

a. for the avoidance of doubt, Section 2(a)(1) grants You the right to extract, reuse, reproduce, and Share all or a substantial portion of the contents of the database for NonCommercial purposes only;

b. if You include all or a substantial portion of the database contents in a database in which You have Sui Generis Database Rights, then the database in which You have Sui Generis Database Rights (but not its individual contents) is Adapted Material; and

c. You must comply with the conditions in Section 3(a) if You Share all or a substantial portion of the contents of the database.

For the avoidance of doubt, this Section 4 supplements and does not replace Your obligations under this Public License where the Licensed Rights include other Copyright and Similar Rights.

Section 5 -- Disclaimer of Warranties and Limitation of Liability.

a. UNLESS OTHERWISE SEPARATELY UNDERTAKEN BY THE LICENSOR, TO THE EXTENT POSSIBLE, THE LICENSOR OFFERS THE LICENSED MATERIAL AS-IS AND AS-AVAILABLE, AND MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND CONCERNING THE LICENSED MATERIAL, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHER. THIS INCLUDES, WITHOUT LIMITATION, WARRANTIES OF TITLE, MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT, ABSENCE OF LATENT OR OTHER DEFECTS, ACCURACY, OR THE PRESENCE OR ABSENCE OF ERRORS, WHETHER OR NOT KNOWN OR DISCOVERABLE. WHERE DISCLAIMERS OF WARRANTIES ARE NOT ALLOWED IN FULL OR IN PART, THIS DISCLAIMER MAY NOT APPLY TO YOU.

b. TO THE EXTENT POSSIBLE, IN NO EVENT WILL THE LICENSOR BE LIABLE TO YOU ON ANY LEGAL THEORY (INCLUDING, WITHOUT LIMITATION, NEGLIGENCE) OR OTHERWISE FOR ANY DIRECT, SPECIAL, INDIRECT, INCIDENTAL, CONSEQUENTIAL, PUNITIVE, EXEMPLARY, OR OTHER LOSSES, COSTS, EXPENSES, OR DAMAGES ARISING OUT OF THIS PUBLIC LICENSE OR USE OF THE LICENSED MATERIAL, EVEN IF THE LICENSOR HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH LOSSES, COSTS, EXPENSES, OR DAMAGES. WHERE A LIMITATION OF LIABILITY IS NOT ALLOWED IN FULL OR IN PART, THIS LIMITATION MAY NOT APPLY TO YOU.

c. The disclaimer of warranties and limitation of liability provided above shall be interpreted in a manner that, to the extent possible, most closely approximates an absolute disclaimer and waiver of all liability.

Section 6 -- Term and Termination.

a. This Public License applies for the term of the Copyright and Similar Rights licensed here. However, if You fail to comply with this Public License, then Your rights under this Public License terminate automatically.

b. Where Your right to use the Licensed Material has terminated under Section 6(a), it reinstates:

1. automatically as of the date the violation is cured, provided it is cured within 30 days of Your discovery of the violation; or

2. upon express reinstatement by the Licensor.

For the avoidance of doubt, this Section 6(b) does not affect any right the Licensor may have to seek remedies for Your violations of this Public License.

c. For the avoidance of doubt, the Licensor may also offer the Licensed Material under separate terms or conditions or stop distributing the Licensed Material at any time; however, doing so will not terminate this Public License.

d. Sections 1, 5, 6, 7, and 8 survive termination of this Public License.

Section 7 -- Other Terms and Conditions.

a. The Licensor shall not be bound by any additional or different terms or conditions communicated by You unless expressly agreed.

b. Any arrangements, understandings, or agreements regarding the Licensed Material not stated herein are separate from and independent of the terms and conditions of this Public License.

Section 8 -- Interpretation.

a. For the avoidance of doubt, this Public License does not, and shall not be interpreted to, reduce, limit, restrict, or impose conditions on any use of the Licensed Material that could lawfully be made without permission under this Public License.

b. To the extent possible, if any provision of this Public License is deemed unenforceable, it shall be automatically reformed to the minimum extent necessary to make it enforceable. If the provision cannot be reformed, it shall be severed from this Public License without affecting the enforceability of the remaining terms and conditions.

c. No term or condition of this Public License will be waived and no failure to comply consented to unless expressly agreed to by the Licensor.

d. Nothing in this Public License constitutes or may be interpreted as a limitation upon, or waiver of, any privileges and immunities that apply to the Licensor or You, including from the legal processes of any jurisdiction or authority.

Creative Commons is not a party to its public licenses. Notwithstanding, Creative Commons may elect to apply one of its public licenses to material it publishes and in those instances will be considered the “Licensor.” The text of the Creative Commons public licenses is dedicated to the public domain under the CC0 Public Domain Dedication. Except for the limited purpose of indicating that material is shared under a Creative Commons public license or as otherwise permitted by the Creative Commons policies published at creativecommons.org/policies, Creative Commons does not authorize the use of the trademark "Creative Commons" or any other trademark or logo of Creative Commons without its prior written consent including, without limitation, in connection with any unauthorized modifications to any of its public licenses or any other arrangements, understandings, or agreements concerning use of licensed material. For the avoidance of doubt, this paragraph does not form part of the public licenses.

Creative Commons may be contacted at creativecommons.org.