A serious knee injury with large osteochondral defect of the femoral condyle and medial patella with loose bodies in the joint. There are kissing-contusions secondary to patella dislocation and a shallow trochlear groove, which has predisposed to patella dislocation during the trauma.

On the initial plain film, there is a fragment of bone adjacent to the tibial spine and a large knee effusion. It would be reasonable to presume that this was a result of an ACL injury. But, it was a fragment of bone from the osteochondral defect and there is no ACL injury.

Its also worth noting that a large effusion juxtaposed to the pad underneath the quadriceps tendon can look like a fat-fluid level. In this case, you would be forgiven for describing a lipohemarthrosis on the lateral radiograph, but there is no fat demonstrated at MRI.