Synovial chondromatosis.
This is a rare benign tumor of the synovium that generates large numbers of cartilaginous mass groups. This tumor accurs most often in the knee. The chondroid bodies may detach from the synovium, grow on their own in the synovial fluid, and subsequently ossify. Ossification is a process in which the fluid turns to a hard substence known as bone. This condition may be associated with swelling of the knee and can produce outpouchings or pockets of the synovium filled with loose bodies, which may commonly be mistaken for cysts.
Clinically, patients typically have a swollen knee joint, pain, mechanical symptoms, and , possibly, a palpable soft-tissue mass that mimics a periarticular cyst(another type of cyst). Calcified lesions are readily identified on routine x-rays, but x-rays may be normal with uncalcified lesions. On MRI, this condition characteristically appears as a highly rounded, cauliflower-like configuration of loose pieces and nodular synovial thickening.
Treatment of Synovial chondromatosis consists of open or arthroscopic removal of the loose bodies and synovectomy.
Cysts about the knee can often be treated as the symptom comes, but if they continue, surgical removal and/or treatment of concurrent pathology may be needed and highly considered.
Conditions that are uncommon can mimic benign cysts and often are indentified by MRI when other more conservative treatment fails. Patients such as these should be referred to specialists who have gained experience in treating such conditions as these.