Instability. Evaluate for ACL tear. MENISCI: The anterior horn and body of the lateral meniscus are intact. The anterior inferior popliteal fascicle appears thickened and indistinct, likely representing injury with mildly increased signal intensity in the adjacent peripheral fibers of the posterior horn of the lateral meniscus, perhaps representing a small undersurface tear in the red zone.There is intrasubstance signal within the posterior horn and body of the medial meniscus which may represent intrasubstance degeneration or perhaps contusion. There is also more vertically oriented linear signal within the red zone of the posterior horn that extends to the tibial articular surface which is suspicious for a small tear. The anterior horn of the medial meniscus is intact.ARTICULAR CARTILAGE AND BONE: Edema within the posterior aspect of the lateral tibial plateau as well as within the lateral femoral condyle above the anterior horn of the lateral meniscus represent bone contusions.A small focus of curvilinear low signal intensity within the subchondral bone of the lateral femoral condyle of the anterior horn of the lateral meniscus likely represents a small impaction fracture.There is prominence of the lateral aspect of the patella which likely represents a partially fused bipartite patella or perhaps old trauma with mild increased signal intensity within the overlying cartilage suggesting focal degeneration, but we see no discrete fluid-filled defect of the articular cartilage.LIGAMENTS: The ACL is thickened, enlarged and of increased signal intensity representing a full-thickness or near full-thickness tear. The PCL, MCL and LCL are intact. EXTENSOR MECHANISM: No significant abnormality noted.ADDITIONAL
1. ACL tear with bone contusions as described above.2. Findings suggestive of small peripheral tears of the posterior horns of the medial and lateral menisci.3. Other findings as above.