MR imaging of the wrist: normal findings that may simulate disease.

Twenty-six normal wrists in young adults were studied with magnetic resonance (MR) imaging. The following conclusions were drawn regarding normal anatomic features: (a) Multiple slips of the abductor pollicis longus tendon simulate longitudinal tears; (b) the extensor pollicis longus and extensor carpi ulnaris tendons normally demonstrate increased signal intensity simulating tendinitis; (c) small quantities of fluid in the extensor tendon sheaths may be normal and not indicative of tenosynovitis; (d) the triangular fibrocartilage normally demonstrates increased signal intensity simulating tears at its radial and ulnar attachment sites; (e) the volar ulnocarpal ligaments are often indistinct, thereby simulating injury; and (f) the median nerve has signal intensity equivalent to that of fat, nor of muscle as commonly believed. Awareness of these normal features is critical in making the correct interpretation of MR images of the wrist.