Complete disruption of medial patellar retinaculum with adjacent periligamentous edema and lateral displacement of patella.
Associated patchy areas of marrow edema is seen involving lateral femoral condyle and medial patellar surface, appearing of low signal on T1 and high signal on T2 and STIR weighted images.
An osteochondral ulcer is seen at the posterior patellar articular surface.
Mild amount of intra-articular synovial effusion is noted.