A rare case of carpal tunnel syndrome due to tenosynovial osteochondroma.

A rare case of carpal tunnel syndrome due to an extra-articular synovial osteochondroma arising from the synovial sheath of the flexor pollicis longus tendon, is described. This has not been described in the literature previously. The cyst with the contained osteochondroma was excised with good relief of symptoms. The histological examination of the osteochondroma revealed another interesting and unusual feature. We would like to document a case of tenosynovial chondrometaplasia of the synovial lining of a tendon sheath. Only a few such cases have been reported in the literature.