trigger thumb
A painful disability in the hand affecting the finger or thumb. It is caused by mechanical impingement of the digital flexor tendons as they pass through a narrowed retinacular pulley at the level of the metacarpal head. Thickening of the sheath and fibrocartilaginous metaplasia can occur, and nodules can form. (From Green's Operative Hand Surgery, 5th ed, p2137-58).