Presentation
Fell on left knee with mild swelling and painful range of motion.
Patient Data
Mild suprapatellar effusion.
The patella is laterally dislocated, with irregular cortical outline at the medial patellar articular facet reflecting osteochondral fracture.
Displaced intra-articular fractured bone fragments of the patella on the lateral aspect of lateral femoral condyle.
Moderate knee joint effusion, with a superficial thin fat layer, reflecting lipohemarthrosis.
Osteochondral avulsion of patellar cartilage at the medial articular facet with fragmentation and displacement lateral to lateral femoral condyle anterior to popliteus tendon insertion.
Associated high-grade partial thickness tear of medial patellar retinaculum.
Bone marrow edema of the inferomedial aspect of the patella and anterolateral aspect of the lateral femoral condyle.
Moderate knee joint effusion, with three different intensity layers reflecting lipohemarthrosis.
Traumatic changes of Hoffa pad of fat.
Wiberg type I patella and no trochlear dysplasia.
Intact cruciate ligaments, collateral ligaments and menisci.
Case Discussion
Classic appearance of lateral patellar dislocation with associated osteochondral injury and intra-articular bodies. The bone marrow edema pattern is called "kissing contusions" involving the inferomedial portion of the patella and the lateral femoral condyle. Images should be scrutinized for the presence of osteochondral injury as this affects the management. In this case, there is no associated abnormal patellar morphology or trochlear dysplasia.
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