Chondromalacia patellae
Updates to Article Attributes
Chondromalacia patellae refers to softening and degeneration of the articular hyaline cartilage of the patella and is a frequent cause of anterior knee pain.
Epidemiology
Tends to occur in young adults. There is a recognised female predilection.
Clinical presentation
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.
Pathology
Associations
Chondromalacia patellae can either occur in isolation or secondary to other conditions, including 1-4:
- direct trauma
- patellar dislocation
- chronic patellar instability/subluxation
- patella alta
- quadriceps imbalance
- synovial plicae 3
Radiographic features
Plain radiograph
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
CT arthrography can be used to diagnose plicae and focal cartilage defects but can be insensitive to early chondral injury 3.
MRI
MRI is the modality of choice for assessing patellar cartilage.
-
T1
- 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 oedema pattern (low signal)
- secondary changes of osteoarthritis may be seen
-
T2/PD
- 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
- the grading system of chondromalacia patellae is based on T2/PD weighted MRI findings and arthroscopic correlation: see chondromalacia grading (Outerbridge method) or modified Noyes
In the absence of effusion, plicae may be difficult to identify 3.
Treatment and prognosis
Non-operative treatment
Initial management is with a reduction of strenuous activities, NSAIDs and exercises to stretch and strengthen quadriceps muscle (especially vastus medialis) 4.
Operative treatment
A variety of operative options exists including 4:
- arthroscopic debridement and lavage: diagnostic but only offers short term symptomatic relief
- articular resurfacing
- surgical correction for instability
- patellectomy
Differential diagnosis
General imaging differential considerations include:
- dorsal defect of the patella: on the superolateral corner of the patella
- bone marrow oedema at the inferior pole as a result of
-<a href="/articles/jumpers-knee-1">jumper knee</a>/<a href="/articles/sinding-larsen-johansson-disease">Sinding-Larsen-Johansson disease</a>- +<a href="/articles/jumpers-knee-1">jumper's knee</a>/<a href="/articles/sinding-larsen-johansson-disease">Sinding-Larsen-Johansson disease</a>
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