Popliteus muscle injury and partial patellar tendon avulsion

Case contributed by Dr Henry Knipe

Presentation

Sustained twist injury with planted foot in collision with another player while playing football.

Patient Data

Age: 12 years
Gender: Male

Large joint effusion. Subcutaneous edema along the medial aspect of the knee. Posterior capsular edema.

No meniscal tear. Cruciate and collateral ligaments are intact. 

Popliteus muscle belly edema and fiber disruption with a tiny intramuscular hematoma adjacent to the myotendinous junction; free tendon is intact. Extensive myofascial edema in the upper calf. No other posterolateral corner injury is demonstrated.

Quadriceps tendon is intact. Partial tear of the patellar tendon involving the distal deep fibers with avulsion and retraction from tibial tuberosity. Edema of the inferior Hoffa's fat pad.

Bone bruise through the non-weightbearing referral medial femoral condyle. No chondral injury.

Osteochondroma with small cartilage cap arising from the medial femoral metaphysics. 

Case Discussion

The mechanism of injury in this case correlates well with the injuries seen:

  • direct blow results in the medial femoral condyle bone bruise and overlying subcutaneous edema
  • popliteus muscle injury presumably the result of an hyperextension-external rotation mechanism of injury
  • hyperextension injury results in the partial patellar tendon avulsion and posterior capsule injury

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