This is an example of secondary synovial osteochondromatosis based on the imaging features of large calcified intra-articular loose bodies of varying sizes, bilateral knee involvement, and background evidence of osteoarthrosis. Other causes include trauma and neuropathic arthropathy. Primary synovial osteochondromatosis which is a differential occurs at a younger age, usually mono-articular, with a finding of smaller intra-articular loose bodies and less degenerative changes.