Synovial chondromatosis is a rare disease of unknown etiology, which arises from hyaline metaplastic transformation of synovial membrane. It is mostly monoarticular and affects large joints of lower extremities. Clinical picture and radiographic findings are indistinguishable from rapidly progressive osteoarthritis at the onset of the disease. In the late course, destruction of joint and bone structures is observed. Presented case report demonstrates difficulties of differential diagnosis in a patient with rheumatoid arthritis in whom the presence of synovial chondromatosis resembled malignant process of joint or pelvis that was resolved by radical surgery firstly by extirpation and subsequently by total hip implants.

        Key words: Synovial chondromatosis, hyaline metaplasia, rheumatoid arthritis