MRI
The joint fluid is filled with innumerable small (3 mm) T1 and T2 hypointense bodies filling and expanding the knee joint with an associated joint effusion. A larger lesion in the suprapatellar bursa likely represents a conglomerate lesion. The nodules bow the anterior cruciate ligament posteriorly. The posterior cruciate ligament has a normal appearance.
The cartilage covering the anterior aspect of the lateral femoral condyle is thinned and irregular. No underlying bone marrow abnormality. Small joint margin osteophytes noted.
Both menisci and collateral ligaments are intact.
The patella is subluxed laterally with an associated defect in the inferior cartilage and high T2 signal surrounding a subchondral cyst. Some of the medial retinacular fibres are avulsed from the patella. Patellar alta noted.
Conclusion:
Innumerable loose bodies with some ossification in the joint space, suspicious for synovial osteochondromatosis.
Degenerative changes with osteophyte formation and lateral femoral condyle cartilage thinning and irregularity.
Changes suggestive of previous lateral patella dislocation with degenerative changes in the patellofemoral compartment.