Primary and secondary synovial chondrometaplasia: histopathologic and clinicoradiologic differences.

One hundred thirty-six cases diagnosed clinically as either synovial chondrometaplasia or osteocartilaginous loose bodies were reviewed. On the basis of the histopathologic peculiarities, the cases were grouped into two distinct categories, primary and secondary synovial chondrometaplasia, comprising 10 and 126 cases, respectively. In each group there was synovial chondrometaplasia but the histologic patterns were dissimilar. In cases of secondary synovial chondrometaplasia the initiating factors were usually obvious and the lesions were nonaggressive. Primary synovial chondrometaplasia, on the other hand, was aggressive and was associated with a high incidence of recurrence.