Presentation
Chronic instability. Previous history of anterior cruciate ligament rupture.
Patient Data
Changes of early osteoarthritis are present in both the knee and patellofemoral joints. Signs of joint effusion.
Moderately large joint expansion with an effusion and quite marked synovial proliferation containing fat deposits consistent with lipoma arborescence.
The anterior cruciate ligament shows chronic tear of its posterolateral bundle, the anteromedial bundle is intact. Posterior cruciate ligament is intact. Medial and lateral collateral ligaments are intact. Medial and lateral menisci are intact.
There is irregular loss of articular cartilage over both the medial and lateral femoral condyles more marked over the lateral femoral condyle with some irregular loss of cartilage of the lateral tibial plateau. Minimal marginal osteophytes of the femoral condyles and tibial plateau with a central osteophyte of the lateral femoral condyle.
Quadriceps tendon and patellar ligament show integrity and normal signal. Full thickness cartilage loss in both facets of the patellofemoral articulation, with subchondral cyst formation.
A bursal cyst emerges posteriorly into the popliteal fossa medial to the medial head of the gastrocnemius muscle. Popliteus tendon sheath is expanded with synovitis and fluid. Posterolateral and medial corners tendons are intact.
Case Discussion
This case illustrates features suggesting tricompartmental osteoarthritis, more marked in the patellofemoral joint and lateral knee compartment. There is also lipoma arborescens that is most likely related to the osteoarthritis or to a chronic inflammatory condition. Findings of a chronic partial tear of the ACL (posterolateral bundle).
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