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Chondromalacia patellae refers to softening and degeneration of the articular hyaline cartilage of the patella that articulates with the trochlear groove of the femur and is a frequent cause of anterior knee pain.
Tends to occur in young adults. There is a recognized female predilection.
Patients with chondromalacia patellae usually present with anterior knee pain on walking up or down stairs. Additionally, there may be knee pain when kneeling, squatting, or after sitting for long periods of time. Knee stiffness, crepitus and effusions may also be present. In some cases, a history of patellar dislocation may be present 4. Some patients may present with quadricep wasting or atrophy 10.
Chondromalacia patellae can either occur in isolation or secondary to other conditions, including 1-4:
chronic patellar instability/subluxation
Plain radiographs of the knee cannot assess for chondral changes directly and can only demonstrate features of osteoarthritis (OA) involving the patellofemoral joint in end-stage disease. A joint effusion may be visible. Lateral and skyline views are more helpful to assess for shallow excavation in the subchondral bone involving the patella.
CT arthrography can be used to diagnose plicae and focal cartilage defects but can be insensitive to early chondral injury 3.
MRI is the modality of choice for assessing patellar cartilage.
a poor sequence for cartilage and surface irregularity and subtle signal change may be inapparent
areas of hypointensity may be seen in cartilage
subchondral reactive bone marrow edema pattern (low signal)
secondary changes of osteoarthritis may be seen
best sequences for assessing cartilage
most patients with chondromalacia patellae have focally increased signal in the cartilage or focal contour defects in the cartilage surface
abnormal cartilage is usually of high signal compared to normal cartilage
findings range from a subtle increase in signal to complete loss of cartilage
In the absence of effusion, plicae may be difficult to identify 3.
Treatment and prognosis
A variety of operative options exists including 4:
arthroscopic debridement and lavage: diagnostic but only offers short term symptomatic relief
surgical correction for instability
General imaging differential considerations include:
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