OBSERVATIONS of four cases of posterior tibial tenosynovitis in which anomalies of the tendon were found at surgical exploration has prompted a review of this subject. The syndrome of noninfectious tenosynovitis was first described by Velpeau, in 1818, and again in 1825.1The work of de Quervain,2in 1895, and of many others since has served to emphasize the importance of this condition as a cause of painful symptoms, particularly about the wrist and ankle. Kulowski,3in 1936, was the first to mention tenosynovitis of the sheath of the posterior tibial tendon. This was also noted by Lipscomb,4who stated that it occurred in about 16% of cases of tenosynovitis and peritendinitis of the feet and ankles. Lapidus and Seidenstein5reported three cases of tenosynovitis with effusion involving the sheath of the posterior tibial tendon. Lipscomb noted anatomic variations of the tendons within the posterior