Tarsal tunnel syndrome caused by an anomalous muscle.

We report the cases of six patients (seven feet) who had tarsal tunnel syndrome in association with an anomalous muscle that was located deep to the flexor retinaculum of the ankle. An accessory flexor digitorum longus muscle was present in six of the ankles and a tibiocalcaneus internus muscle, in one. All of the patients had a release of the tarsal tunnel and a neurolysis of the posterior tibial nerve and its branches in addition to a resection of the anomalous muscle. The duration of follow-up averaged forty-one months (range, twenty-eight to eighty-three months). Although the pain was reduced in four of the six patients, only one patient was completely free of symptoms at the time of the most recent follow-up examination. Four of the six patients were satisfied with the result of the operation.