CT and MR imaging depict the extent of the synovial disease (particularly surrounding soft-tissue involvement) and lobular growth. These signal intensity characteristics on MR images and low attenuation of the nonmineralized regions on CT scans reflect the high water content of the cartilaginous lesions. Magnetic resonance (MR) imaging findings are more variable, depending on the degree of mineralization, although the most common pattern (77% of cases) reveals low to intermediate signal intensity with T1-weighting and very high signal intensity with T2-weighting with hypointense calcifications. Computed tomography (CT) optimally depicts the calcified intraarticular fragments and extrinsic bone erosion.

Extrinsic erosion of bone is seen in 20%–50% of cases. Radiographs reveal multiple intraarticular calcifications (70%–95% of cases) of similar size and shape, distributed throughout the joint, with typical “ring-and-arc” chondroid mineralization. Radiologic findings are frequently pathognomonic. The pathologic appearance may simulate chondrosarcoma because of significant histologic atypia, and radiologic correlation to localize the process as synovially based is vital for correct diagnosis. The knee, followed by the hip, in male adults are the most commonly involved sites and patient population. The nodules may enlarge and detach from the synovium.

Primary synovial chondromatosis represents an uncommon benign neoplastic process with hyaline cartilage nodules in the subsynovial tissue of a joint, tendon sheath, or bursa.

Synovial fluid image