Patients › Knee

Distal femur fracture

Updated Sep 2026

What you're feeling¶

A broken lower end of the thigh bone, just above the knee, hurts where the break is. The pain is usually sharp at first and settles into a deep ache. Standing, putting weight on the leg, bending the knee and twisting on that leg all make it worse. Resting with the leg still and supported eases it.

The ache often flares at night and first thing in the morning, and it can throb after you have been on your feet. Even small movements of the knee can hurt, because the break sits right where the thigh bone meets the knee joint. Some people feel the knee is unstable, as if it will not hold them.

Day to day, the leg is hard to use. Walking any distance, climbing stairs, getting out of a low chair and stepping into the shower all become difficult. You may need crutches or a frame, and carrying things while walking is a struggle. Sleeping on that side, driving and getting in and out of the car can also be a problem.

This injury is more common in older adults, especially women after 60, and often happens when the bone is already thin. In older people it can be a serious injury. About 1 in 4 people over retirement age with this fracture do not survive the year after it, and medical problems after surgery are common in this age group. That is one reason surgery is usually recommended: holding the bone still lets you get up and moving early, which matters for your health and independence.

Recovery takes time. Even with modern treatment, the leg may not feel fully back to normal at one year, and the effect of the injury on your quality of life can last up to 12 months. Your knee and hip movement generally returns over time.

What's actually happening¶

The thigh bone has a wide shaft and a lower end that widens into two rounded knobs, one on each side of the knee. These knobs form half of the knee joint and are covered in smooth cartilage so the joint glides. A distal femur fracture is a break in this lower end, just above the knee. When the bone breaks here, the rough broken edges and any shift in the bone's position are what cause the sharp pain and the feeling that the knee will not hold you.

The break can also affect how the knee lines up. The two knobs need to sit level with each other for weight to pass evenly through the joint. If a break lets one side drop or the joint surface step out of place, weight is carried unevenly, which can wear the cartilage faster over time. The knee is also held together by strong straps called ligaments, and these anchor to the very part of the bone that has broken, so the joint can feel loose until the bone is held still.

This injury is uncommon, making up about 0.5% of all fractures. It happens more often in older adults, especially women, because the bone is often thinner by then. In younger people it usually takes a big force, such as a car crash or a fall from height. In older people it can happen from a simple fall onto the leg.

Because the bone is broken into pieces that have shifted, it rarely stays put on its own. That is why surgery is usually advised: the bone is held in the correct position with a plate or rod and screws while it knits together. Holding the pieces still also lets you start moving the knee early, which helps prevent stiffness. The main risks of this injury are that the bone fails to knit at all, or knits in a poor position, and these risks are higher when bone quality is poor.

What we can do about it¶

Before any decision, we work out the exact pattern of the break. Plain X-rays are the usual first step. Sometimes X-rays are taken without putting weight through the leg, because this shows the injury without risking further shift in the bone. A CT scan, which builds detailed pictures from X-rays, can show the fracture lines and any displacement in the knee. For complex breaks that run into the joint surface, a three-dimensional CT reconstruction can help with planning the operation.

For most people with this fracture, holding the bone still with surgery is the treatment. The aim is to line the broken pieces up correctly and keep them there while the bone knits together. This is done with metal implants, most often a rod placed down the hollow centre of the thigh bone, or a plate and screws along the outside of the bone. The choice depends on the fracture pattern, your bone quality and your knee. If the break has broken the skin, an external frame can hold the bone from outside while the soft tissues settle. When a previous knee or hip replacement is nearby, we plan the fixation so it grips enough healthy bone above and below the fracture.

Some breaks are simple, with one clean split between two pieces. In these cases a screw across the split can hold the gap closed, which helps the bone knit faster. If the bone is broken into several pieces, a second plate on the other side of the bone is sometimes added. This can improve knee movement at 6 months, reduce complications overall, and lower the chance of the bone healing in a poor position.

If the bone fails to knit, more surgery may be needed. This can mean adding a plate alongside the existing rod, sometimes with a graft of your own bone to help the break heal. Preserving the blood supply at the fracture site guides how we do this.

What to expect¶

Most broken lower ends of the thigh bone are treated with surgery, and holding the bone still lets you start moving early. With modern treatment, your knee and hip movement generally returns over time. But recovery is a long road. The effect of this injury on your quality of life can last up to 12 months, and even then the leg may not feel fully back to normal.

Healing itself takes months, not weeks. For fractures of the thigh bone treated with a rod down the centre, the bone usually knits in around 18 weeks, though some people need longer than 25 weeks. If the bone is slow to knit or fails to knit at all, further surgery can help it heal, and that healing also takes months.

The main things that can go wrong are that the bone fails to knit at all, or knits in a poor position. This risk is higher when the bone is thin, and in people over 70 with a break that runs into the knee joint, close to 1 in 5 develop a nonunion. When a knee or hip replacement is nearby, about 18% develop a nonunion and roughly 1 in 4 have some complication. If infection or nonunion does happen, it can become a long-term condition for nearly a quarter of the people affected.

Leaving the break alone is rarely an option. Without surgery, the bone rarely stays in place on its own, and lying still for weeks brings its own problems, which is why surgery is usually advised. In older adults this injury is serious: about 1 in 4 people over retirement age do not survive the year, and medical problems after surgery are common in that age group.

The realistic picture is this. With treatment, most people regain their knee and hip movement over time, though the leg may not feel fully normal for up to a year. Some need more surgery along the way. Your surgeon will watch your healing with X-rays and tell you how your bone is knitting at each review.

When to see someone¶

This injury usually announces itself. The pain is sudden and severe, and the leg may not take weight, so most people go straight to an emergency department. Go to an emergency department if you have had a fall or a blow to the thigh and the pain is severe, the leg looks bent or shortened, or you cannot stand on it. Go straight away if the broken bone has pushed through the skin. Ask for a specialist review if you have had a knee or hip replacement before and you now have sudden pain just above the knee, because a break around a replacement needs urgent assessment. In older adults this injury is serious: about 1 in 4 people over retirement age do not survive the year, so do not wait to see whether it settles.

Evidence & references

This is the clinical evidence summary written for health professionals. It is technical, and it lists the research this page was built from. You do not need to read it to understand your treatment or to make a decision about it.

Anatomy & Pathophysiology¶

Bony Anatomy¶

The bones of the knee are the distal femur, the proximal tibia, and the patella [1].
The medial femoral condyle is larger and projects farther posteriorly and distally than the lateral condyle [4].
The medial epicondyle is the most anterior and distal osseous prominence of the medial femoral condyle [4].
The adductor tubercle is located proximal and posterior to the medial epicondyle [4].
The gastrocnemius tubercle is located slightly distal and posterior to the adductor tubercle [4].
The lateral femoral condyle projects farther anteriorly than the medial condyle [4].
The lateral femoral condyle is wider in the medial-lateral direction than the medial femoral condyle [4].
The sulcus terminalis is a small ridge on the lateral femoral condyle just distal to the intercondylar notch that separates the patellofemoral and tibiofemoral articular surfaces [4].
The trochlear groove separates the femoral condyles anteriorly and constitutes the patellofemoral articulation [4].
The intercondylar notch is of variable width and is the site of attachment of the cruciate ligaments [4].
The tibial articular surface slopes 7° to 10° in the sagittal plane [4].
The medial tibial plateau is larger than the lateral plateau and is concave in its frontal and sagittal planes [4].
The lateral tibial plateau is smaller and more circular than the medial plateau, concave in the frontal plane, and convex in the sagittal plane [4].
The medial and lateral tibial plateaus are separated by the intercondylar eminence and its medial and lateral spinous processes [4].
The tibial tuberosity is the site of attachment of the patellar tendon and is typically located in the midline anteriorly but may be slightly lateral [4].
Gerdy’s tubercle is the insertion site of the iliotibial band and is located 2 to 3 cm lateral to the tibial tubercle on the proximal tibia [4].
The proximal fibula articulates with a facet of the lateral cortex of the tibia and is not part of the knee articulation [4].
The patella is the largest sesamoid bone in the body and averages 2.5 cm in thickness [4].
The patella has the thickest articular surface in the body, approximately 5 mm in the midportion and 2 mm on the sides [4].
The patellar articular surface contains a vertical, central ridge that separates the broader lateral facet from the medial facet, and a smaller, more medial facet called the odd facet [4].
The posterior slope of the medial tibial plateau is a mean of 10.7° and the lateral plateau is a mean of 7.2° [18].
The fibular head is located a mean of 1.5 cm distal to the joint line, with a range of 6 to 32 mm [18].
The medial femoral condyle has a large, convex articular surface [18].
The lateral femoral condyle has a broader mean anterior-posterior dimension than the medial femoral condyle, which allows internal rotation of the distal femur with knee extension [18].
The lateral femoral condyle has a broader mean medial-lateral dimension than the medial condyle [18].
The lateral trochlear facet resists lateral subluxation of the patella [18].
The sulcus terminalis is a transverse ridge extending from the oblique facets of the femoral trochlea that is deeper on the lateral condyle than on the medial condyle [18].
The PCL inserts on the anteromedial wall of the intercondylar notch and the ACL inserts on the posterolateral wall [18].
The patella has three facets: lateral, medial, and odd [18].
The odd facet is a small facet on the distal medial patella that articulates in deep flexion of the knee [18].

Vascular and Nerve Anatomy¶

The blood supply to the knee is formed from an anastomosis around the knee derived from the descending geniculate artery, medial and lateral superior geniculate arteries, medial and lateral inferior geniculate arteries, middle geniculate artery, and anterior tibial recurrent arteries [4].
The middle geniculate artery supplies both the anterior and posterior cruciate ligaments [4].
The inferior geniculate arteries pass deep to their respective collateral ligaments [4].
The blood supply of the patella is derived from the geniculate artery complex with some contribution from the anterior tibial recurrent artery and primarily exists in the middle to inferior portions of the patella [4].
The knee is innervated by branches of the femoral nerve (L2, L3, L4), obturator nerve (L2, L3, L4), and sciatic nerve (L4, L5, S1, S2) [4].
The largest nerve providing innervation of the intra-articular knee is the posterior articular branch of the tibial nerve [4].
The posterior articular branch of the tibial nerve supplies the infrapatellar fat pad, the synovial covering over the cruciate ligaments, and the periphery of the meniscus [4].
Nerves to the cruciate ligaments contain vasomotor and pain fibers as well as mechanoreceptors that may be involved in proprioception [4].
The infrapatellar branch of the saphenous nerve arises proximal to the knee joint medially and crosses distal to the patella to innervate the skin over the region of the anterior knee and proximal tibia [4].
The popliteus artery travels through the adductor hiatus, where it is relatively immobile, and distally through the fibrous arch deep to the soleus muscle [24].
The common peroneal nerve travels along the posterior edge of the biceps femoris and continues distally around the fibular neck [24].
The tibial nerve, after branching from the sciatic nerve, courses distally through the center of the popliteus fossa [24].

Ligaments¶

The anterior cruciate ligament (ACL) travels from the medial border of the lateral femoral condyle to its insertion site anterolateral to the medial tibial spine [1].
The ACL prevents anterior translation and rotation of the tibia on the femur [1].
The posterior cruciate ligament (PCL) prevents posterior subluxation of the tibia on the femur [1].
The PCL runs from the lateral aspect of the medial femoral condyle to the posterior aspect of the tibia, just below the joint line [1].
The medial collateral ligament has superficial and deep portions which stabilize the knee to valgus stresses [1].
The lateral collateral or fibular collateral ligament runs from the lateral femoral condyle to the head of the fibula [1].
The lateral collateral ligament is the main stabilizer against varus stress [1].
The lateral collateral ligament is part of the posterolateral “complex” or “corner” of the knee that also resists external rotation [1].
The popliteofibular ligament is present in 90% of knees and runs from the tendon of the popliteus muscle to the styloid on the posterior fibular head [1].
The ACL is composed of 90% type I collagen and 10% type III collagen [4].
The mean length of the ACL is 33 mm and the mean midsubstance width is 11 mm [4].
The femoral attachment of the ACL is a semicircular area (20 mm long and 10 mm wide) on the posteromedial aspect of the lateral femoral condyle [4].
The tibial attachment of the ACL is a broad, irregular, oval-shaped area (30 mm long and 10 mm wide) slightly medial and anterior to the midline and between the medial and lateral tibial spinous processes [4].
The ACL is an intra-articular ligament but technically extrasynovial as it is surrounded by synovium [16].
The ACL has a variable length of 22 to 41 mm and width of 7 to 12 mm, consistently narrowest in the midsubstance [16].
The femoral origin of the ACL is on the posteromedial edge of the lateral femoral condyle, posterior to the lateral intercondylar ridge (Resident’s ridge) [16].
The ACL attachment is usually oval in shape, with the anteromedial bundle arising from the superior and anterior aspects and the posterolateral bundle arising from the posterior and inferior aspects [16].
The ACL bundles are often separated by the lateral bifurcate ridge, which runs from anterior to posterior on the femur [16].
The bulk of the ACL anteromedial bundle is attached between 9.30 and 11.30 o'clock and the posterolateral bundle between 8.30 and 10 o'clock on a clock-face description based on the posterior outlet of the femoral intercondylar notch [16].
The distance on the femur between the centers of the ACL bundles varies from 8 to 10 mm [16].
The tibial footprint of the ACL is on the tibial plateau in the anterior intercondylar fossa, between the medial and lateral tibial spines [16].
The tibial insertion of the ACL is 120% larger than the femoral insertion [16].
The ACL anteromedial bundle is tight in knee flexion and the posterolateral bundle is tight in extension [4].
The ACL anteromedial bundle is primarily an anterior restraint evaluated by Lachman and anterior drawer tests [5].
The ACL posterolateral bundle is primarily a rotatory restraint evaluated by pivot shift test [5].
The ACL is typically subjected to peak loads of 170 N during walking and up to 500 N with running [19].
The ultimate strength of the ACL in young patients is about 1750 N [19].
The ACL fails by serial tearing at 10% to 15% elongation [19].
The PCL has a mean length of 38 mm and mean width of 13 mm [18].
The PCL has a broad, crescent-shaped femoral attachment on the anterolateral medial femoral condyle with a mean length of 30 mm and mean width of 5 mm [18].
The tibial insertion of the PCL onto the posterior central sulcus is 10 to 15 mm distal to the joint line of the knee [18].
The PCL anterolateral bundle is stronger and stiffer than the posteromedial bundle and is tight in knee flexion [18].
The PCL posteromedial bundle is tight in knee extension [18].
Sectioning the PCL increases contact pressures in the medial compartment and the patellofemoral joint [19].
The superficial medial collateral ligament (sMCL) proximal division resists valgus tibial translation and tibial external rotation [5].
The sMCL distal division resists tibial external rotation in knee extension and tibial internal rotation [5].
The deep MCL resists valgus translation and tibial internal and external rotation [5].
The posterior oblique ligament resists tibial internal rotation, especially in knee extension, and tibial external rotation [5].
The lateral collateral ligament resists varus tibial translation and tibial external rotation, especially at 30 degrees of knee flexion [5].
The popliteus tendon resists tibial external rotation, especially in knee flexion, and varus tibial translation [5].
The popliteofibular ligament resists tibial external rotation, especially in knee flexion, and posterior tibial displacement [5].
The oblique popliteal ligament resists knee hyperextension and varus tibial translation [5].
The joint capsule and the collateral ligaments are the principal extraarticular static stabilizing structures [7].
The capsule is a sleeve of fibrous tissue extending from the patella and patellar tendon anteriorly to the medial, lateral, and posterior expanses of the joint [7].
The medial capsule is more distinct and well defined than its lateral counterpart [7].
The anteromedial and anterolateral portions of the capsule are relatively thin structures but are reinforced by the medial and lateral patellar retinacular expansions [7].
The medial patellofemoral ligament runs from the patella near the junction of the middle and superior thirds to the medial femoral epicondyle [7].
The posteromedial corner of the knee has five major components: the posterior oblique ligament, the semimembranosus tendon and its expansions, the oblique popliteal ligament, the posteromedial joint capsule, and the posterior horn of the medial meniscus [13].
The posterior oblique ligament is attached proximally to the adductor tubercle of the femur and distally to the tibia and posterior aspect of the capsule [13].
The distal attachment of the posterior oblique ligament is composed of three arms: the tibial arm, the capsular arm, and the distal arm [13].
The central portion of the posterior oblique ligament is the thickest and probably the most important arm, originating in the region of the adductor tubercle [13].
The semimembranosus tendon has five expansions: the direct arm, the anterior or deep arm, the arm to the posterior oblique ligament, the arm to the oblique popliteal ligament, and the expansion to the popliteus aponeurosis [13].
The oblique popliteal ligament is a broad fascial band originating from the capsular arm of the posterior oblique ligament and the lateral expansion of the semimembranosus to cross the posterior aspect of the knee [13].
The posteromedial capsule begins posterior to the superficial and deep MCL, with the deep MCL blending with and becoming inseparable from the central arm of the posterior oblique ligament [13].
The posteromedial portion of the medial capsular ligamentous complex is especially important for valgus and rotational stability to the knee [13].
The central arm of the posterior oblique ligament must be tightened in surgical repair or reconstruction, or passive stability cannot be attained regardless of any other surgical procedures [13].

Menisci¶

The menisci are C-shaped fibrocartilaginous disks in the knee that provide shock absorption, allow for increased congruency between joint surfaces, enhance joint stability, and aid in distribution of synovial fluid [1].
The medial and lateral menisci provide a concave surface with which the convex femoral condyles can articulate [1].
Without menisci, the convex femoral condyles articulate with the relatively flat tibial plateaus, decreasing surface area of contact and increasing pressure on the articular cartilage [1].
The medial meniscus is firmly attached to the joint capsule along its entire peripheral edge [1].
The lateral meniscus is attached to the anterior and posterior capsule, but there is a region posterolaterally where it is not firmly attached [1].
The medial meniscus has less mobility than the lateral meniscus and is more susceptible to tearing when trapped between the femoral condyle and tibial plateau [1].
The lateral meniscus is larger than the medial meniscus and carries a greater share of the lateral compartment pressure than the medial meniscus carries for the medial compartment [1].
The knee menisci are wedge-shaped fibrocartilaginous structures situated between the femoral condyles and tibial plateau [14].
The medial meniscus has a semicircular shape, which covers approximately 50% to 60% of the medial tibial plateau in adulthood [14].
The posterior horn of the medial meniscus averages 11 mm in the anterior-posterior dimension, whereas the anterior horn is narrower [14].
The anterior horn of the medial meniscus attaches to the tibia anterior to the ACL near the intercondylar fossa [14].
The transverse, or intermeniscal, ligament connects the anterior horns of the medial and lateral menisci [14].
The posterior root attachment of the medial meniscus lies in the posterior intercondylar fossa between the lateral meniscus and PCL [14].
The meniscotibial (coronary) ligament stabilizes the medial meniscus through its attachment from the inferior aspect of the posterior horn to the tibia [14].
The medial meniscus is firmly attached to the deep medial collateral ligament and joint capsule, limiting its mobility [14].
The lateral meniscus has a more circular C-shape with symmetric sizes of the anterior and posterior horns [14].
The lateral meniscus anterior root attaches anterior to the intercondylar eminence and just lateral to the ACL insertion site on the tibia [14].
The lateral meniscus posterior root attaches posterior to the lateral tibial spine just anterior to the medial meniscus posterior root [14].
The popliteomeniscal fascicles extend from the lateral meniscus to the posterior capsule to create the popliteal hiatus [14].
The meniscofemoral ligaments are variably present structures which connect the posterior horn of the lateral meniscus to the medial femoral condyle [14].
The ligament of Humphrey crosses anterior to the PCL and the ligament of Wrisberg crosses posteriorly [14].
The less continuous attachment of the lateral meniscus to the capsule allows for

Investigations¶

Plain Radiography¶

Plain radiographs are appropriate initial imaging studies for most knee conditions because they allow the assessment of traumatic injury, arthritis, patellofemoral alignment, osteochondral injury, bone neoplasm, and surgical implants [22].
Imaging studies should include at least two perpendicular views: AP and lateral [22].
Weight-bearing AP (extension) views are used to assess cartilage loss from the distal femur and tibial plateau [22].
Weight-bearing PA (Rosenberg; flexion) views are used to assess cartilage loss from the posterior femur and tibial plateau [22].
Patellofemoral views are used to assess patellofemoral alignment (tilt/subluxation), patellar and trochlear morphology, osteochondral injury, and patellofemoral arthritis [22].
Notch views are used to assess posterior femoral cartilage, notch width, and osteophytes [22].
Non–weight-bearing radiographs may identify acute injury without the risk of fracture displacement in trauma cases [22].
Radiographs should be inspected for acute fracture, lateral capsular avulsion (Segond fracture), loose bodies, Pellegrini-Stieda lesion (MCL calcification), and evidence of patellar dislocation [10].
Stress radiographs should be obtained in patients prior to skeletal maturity to rule out an epiphyseal fracture [10].
Radiographs can underestimate isolated chondral lesions but may demonstrate joint space narrowing, osteophytes, sclerosis, and cysts [26].
Weight-bearing AP and lateral views and an axial view of the patellofemoral joint should be reviewed for articular cartilage evaluation [26].
The ability to detect subtle narrowing or an isolated chondral defect on the flexion surface may be improved with a semiflexed PA view [26].
Long leg alignment views are used to determine the mechanical axis [26].
If the mechanical axis traverses the involved compartment (varus knees with medial compartment lesions or valgus knees with lateral compartment lesions), realignment may need to be considered as an initial procedure or as an adjunct to a cartilage restorative procedure [26].
Radiographs are still the standard for initial evaluation of knee arthritis [30].
Images for knee arthritis evaluation should include weight-bearing AP and lateral views, a view of the weight-bearing knee flexed at 45-degree angle imaged posterior to anterior, a sunrise view (Merchant view), extension and flexion lateral views, and a standing full-length AP radiograph [30].
A standing full-length AP radiograph from hip joint to ankle joint is used to evaluate limb alignment and knee deformity and to identify femoral and/or tibial bone deformity [30].
Radiographs should be inspected for acute fractures, lateral capsular avulsion (Segond fracture), loose bodies, fibular head avulsions, and evidence of patellar dislocation in suspected LCL injuries [31].
With chronic posterolateral instability, degenerative changes of the lateral compartment are often noted on radiographs, including lateral joint space narrowing with osteophytes and subchondral sclerosis [31].
Stress radiographs can help to better quantify the amount of varus angulation present in LCL injuries [31].

Computed Tomography¶

Computed tomography provides a three-dimensional study with ionizing radiation that provides enhanced bone detail [22].
Imaging in the axial, sagittal, and coronal planes may help visualize fracture lines and displacement, osteolytic lesions around joint arthroplasty, and cortical disruption in cases of infection or neoplasia [22].
Three-dimensional reconstructions may help with preoperative planning for complex intra-articular fractures, multiplanar osteotomy for limb malalignment, and reconstitution of bone loss in joint arthroplasty [22].
Axial plane imaging of the hip and knee can help assess the rotational alignment of components of a total knee arthroplasty in cases of patellar maltracking [22].
Three-dimensional CT with remodeling is used for preoperative planning for reconstruction associated with dysplasia, post-trauma planning, and complex total knee arthroplasty (TKA) planning [30].

Magnetic Resonance Imaging¶

Increasing strength of the magnetic field (measured in Tesla units) increases the resolution of images [22].
An injected contrast agent (intravenous or intra-articular) may help delineate specific tissues of interest in MRI [22].
MRI may identify the presence of edema, intra-articular fluid, disruption of ligament fibers, and an atypical ligament contour to suggest cruciate ligament injury [22].
MRI can identify patterns of meniscal injury by location (anterior, midbody, posterior, peripheral, articular), pattern (horizontal, longitudinal, radial, complex), and displacement [22].
MRI may identify the degree of articular cartilage injury (chondrosis, full-thickness cartilage loss), the presence of associated bone marrow edema, and the location (medial condyle, lateral condyle, trochlea, patella; anterior, posterior) [22].
MRI may identify edema, avulsion, or discontinuity for the MCL/lateral collateral ligament (LCL) or associated posteromedial and posterolateral ligamentous complexes [22].
MRI may be used to assess the continuity of the quadriceps or patellar tendon [22].
MRI may be used to assess the margin of resection for a neoplasm, identify vascular malformation, or define the location of nerves or vessels relative to popliteal cysts [22].
MRI is useful for confirming MCL injury and identifying the site of injury [10].
MRI is useful to detect the presence of meniscal and other injuries to the knee in MCL injuries [10].
Relative indications for an MRI in MCL injuries include an uncertain ACL status despite multiple examinations, evaluation of a suspected meniscal tear, or preoperative evaluation for a planned MCL reconstruction or repair [10].
MRI is often a useful adjunct for diagnosing posterolateral corner and LCL injuries in the severely injured knee [31].
MRI findings can refocus the examination to the posterolateral structures when posterolateral injury can often go unnoticed during an initial evaluation [31].
MRI is not indicated if the joint space is significantly narrowed on radiograph in the arthritic patient population [30].
MRI is used when osteonecrosis is suspected in the arthritic patient population [30].
MRI can be used to evaluate articular cartilage morphology [26].

Nuclear Medicine¶

Nuclear medicine involves labeled radionuclide injection followed by delayed imaging of gamma radiation, where areas of increased radionuclide concentration appear bright or “hot” [22].
Nuclear medicine provides a nonspecific study that does not define the etiology of an abnormality but rather the presence of an abnormality that may correlate with a clinical concern [22].
Increased radionuclide activity in bone may be a normal postoperative finding for up to 6 to 12 months after a fracture repair or arthroplasty [22].
Technetium-99 (Tc-99) is a radionuclide that may help identify infection, neoplasia, occult fracture, bone healing, active phases of heterotopic ossification, implant loosening, or failure of osseointegration [22].
Gallium-67 (Ga-67) is a radionuclide that may help differentiate between aseptic and septic prosthetic loosening; 24 to 72 hours are needed for a complete study [22].

Physical Examination¶

The physical examination begins with observation of the patient’s gait, followed by examination of the uninjured knee as a basis of comparison with the injured knee [1].
Any swelling or effusion should be noted during physical examination [1].
A small effusion will cause obliteration of the recesses on the medial and lateral aspects of the patellar tendon; with a larger effusion, diffuse swelling is present in the region of the suprapatellar pouch [1].
A fluid wave can be palpated on the sides of the patella [1].
Active and then passive range of motion is tested carefully during physical examination [1].
The knee is palpated to define areas of localized tenderness [1].
The joint lines are located at the level of the inferior pole of the patella when the knee is flexed to 90 degrees [1].
Laxity to valgus stresses is assessed by the amount of medial joint space opening that occurs at 30 degrees of flexion for MCL injuries [10].
Zero opening is considered normal, with 1-4 mm indicating a grade I injury, 5–9 mm indicating a grade II injury, and 10–15 mm indicating a complete or grade III injury for MCL injuries [10].
Grade I and II MCL injuries typically have a firm end point, whereas a grade III injury tends to have a soft end point to valgus stress [10].
The integrity of the LCL is assessed by placing a varus stress, with the knee in full extension and 30 degrees of flexion [31].
The average baseline for varus opening is 7 degrees [31].
Exam findings with an isolated LCL injury should include varus laxity at 30 degrees of flexion and no instability in full extension [31].
The dial test is performed by externally rotating each tibia and noting the angle subtended between the thigh and the foot at 30 and 90 degrees of flexion [31].
A significant difference in the dial test is an angle 5 degrees or greater than the contralateral leg [31].
Injury to the posterolateral capsule alone is confirmed with greater external rotation at 30 degrees, an isolated PCL at 90 degrees, and to both structures when there is greater rotation at 30 and 90 degrees compared to the uninjured leg [31].
A careful neurovascular examination should be performed as the incidence of neurovascular injury, particularly peroneal nerve injury, has been reported in 12–29% of posterolateral knee injuries [31].
An examination under anesthesia can be valuable when physical examination is unreliable because of the patient guarding the knee [10].
Diagnostic arthroscopy can be used to evaluate for coexisting pathology, though both examination under anesthesia and diagnostic arthroscopy have largely been replaced by MRI [10].
An examination while the patient is relaxed under general anesthetic is extremely useful, particularly in the acute setting for multiligamentous knee injuries [31].

Treatment¶

Substantial improvements in implant design and understanding the determinants of achieving a good clinical outcome have been achieved in the management of distal femur fractures [3].
The evaluation and management of distal femur fractures require an understanding of the injury mechanism, potential associated injuries, and radiographic and clinical goals [3].
Surgical management of distal femur fractures requires a clear understanding of the unique anatomy of the distal femur [3].
Surgical management of distal femur fractures requires comprehensive knowledge of the implant and how it can be used in a biologic-preserving manner to achieve an anatomic reduction and enable fracture healing [3].
Understanding the unique anatomy of the distal femur is necessary to achieve an anatomic reduction [3].
Understanding the unique anatomy of the distal femur is necessary for successful maintenance of reduction using modern implants [3].
Clinical and radiographic assessment of both soft-tissue and osseous injury to the distal femur helps define surgical treatment options [3].
An understanding of expected outcomes and potential postoperative complications related to the surgical management of distal femur fractures is important for optimal results [3].

References¶

[1] A Lange Medical Book Current Diagnosis Treatment In Orthopedics Fifth Edition. 3Sports Medicine > Image KNEE INJURIES.

[3] Orthopaedic Knowledge Update Trauma. Fractures of the Distal Femur > Summary.

[4] Aaos Comprehensive Orthopaedic Review 3. Anatomy and Biomechanics of the Knee > I. Anatomy.

[5] Miller S Review Of Orthopaedics. SECTION 1 KNEE > ANATOMY (FIG. 4.1).

[7] Campbell S Operative Orthopaedics 4 Volume Set. EXTRAARTICULAR LIGAMENTOUS STRUCTURES.

[10] A Lange Medical Book Current Diagnosis Treatment In Orthopedics Fifth Edition. 3Sports Medicine > 1. Medial Collateral Ligament Injuries.

[13] Campbell S Operative Orthopaedics 4 Volume Set. POSTEROMEDIAL CORNER.

[14] Orthopaedic Basic Science Fifth Edition Print Ebook. Biology and Mechanics of the Skeletal Extracellular Matrix > Gross Anatomy.

[16] Rockwood And Green S Fractures In Adults. 59: Patellar Fractures and Dislocations and Extensor Mechanism Injuries > Anterior Cruciate Ligament Anatomy.

[18] Aaos Comprehensive Orthopaedic Review 3. Radiographic Evaluation and Surgical Anatomy of the Knee > II. Surgical Anatomy of the Knee.

[19] Miller S Review Of Orthopaedics. ARTHRODESIS PERSON > Kinetics.

[22] Aaos Comprehensive Orthopaedic Review 3. Radiographic Evaluation and Surgical Anatomy of the Knee > I. Radiographic Evaluation.

[24] Aaos Comprehensive Orthopaedic Review 3. Knee Dislocations and Patellar Fractures* > I. Knee Dislocations.

[26] Aaos Comprehensive Orthopaedic Review 3. Articular Cartilage Injury and Treatment > IV. Full-Thickness Outerbridge Grade IV Defects.

[30] Miller S Review Of Orthopaedics. SECTION 16 PATELLAR TRACKING IN TOTAL KNEE ARTHROPLASTY > SECTION 11 KNEE ARTHRITIS ASSESSMENT.

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