Female, 14 years old. Lateral subluxation of patella. Knee instability. MENISCI: The menisci appear normal.ARTICULAR CARTILAGE AND BONE: There are rounded foci of heterogeneous subchondral signal intensity within the lateral femoral condyle, likely representing the site of microfracture of the osteochondral lesion seen on the prior outside study. There is mild edema and cyst formation in the adjacent marrow. The signal intensity of the overlying articular cartilage is heterogeneous, but we see no frank fluid-filled defect. The remaining articular cartilage appears normal. Subjectively the femoral trochlea is shallow superiorly with asymmetry of the facets (lateral > medial) suggesting mild trochlear dysplasia. Currently, patellofemoral alignment is normal.LIGAMENTS: The cruciate and collateral ligaments are intact. A thin irregular low signal intensity structure can be followed from the vicinity of the abductor tubercle to the superomedial patella which may represent the medial patellofemoral ligament; however, given its irregular appearance, we cannot exclude scar tissue in the vicinity of the of the ligament from old injury. EXTENSOR MECHANISM: The quadriceps and patellar tendons are intact. Portions of the lateral retinaculum are not well seen, likely due to prior release. The tibial tubercle-trochlear groove distance is approximately 18 mm which is borderline abnormal. The Insall-Salvati ratio is 1.2 which is within normal limits.ADDITIONAL
1.Findings of mild femoral trochlear dysplasia and borderline elevated tibial tubercle-trochlear groove distance as well as irregularity of the medial patellofemoral ligament; these findings may be associated with patellofemoral instability.2.Surgical changes of lateral femoral condyle microfracture.