Report of an unusual case of trigger finger secondary to phalangeal exostosis.

Trigger finger is commonly secondary to stenosing tenosynovitis. Space occupying lesions in the tendon bed, although uncommon, may prevent smooth tendon gliding. These include lipoma, anomalous muscle insertions, tumours of the tendon sheath and haemangiomas. We describe a patient who had triggering of the left middle finger at the proximal interphalangeal joint due to an exostosis blocking the flexor tendons gliding. Removal of the exostosis relieved the problem. The clinician must be aware that there are other causes for triggering. These may be identified with pertinent findings in the history and physical examination.