Sprain of the pisiform triquetral joint is a definite clinical entity. It presents as a "tenosynovitis" of the flexor carpi ulnaris muscle from which it can be distinguished by the tests described. The disability in most cases is such that operation is justifiable. Fusion of the pisiform-triquetral joint is preferred to excision of the pisiform because it restores stability to the wrist with the least disturbance to related structures.