Flexor digitorum accessorius longus muscle: an etiology of tarsal tunnel syndrome?

During routine lower extremity laboratory dissection at the Ohio College of Podiatric Medicine, an anomalous muscle, the flexor digitorum accessorius longus was uncovered on one male and one female cadaver. The muscles were located in the deep posterior compartment of the leg and were of differing sizes and origins. This anomalous muscle has been implicated as an etiology for tarsal tunnel syndrome. In cases of tarsal tunnel syndrome that undergo surgical decompression, the flexor digitorum accessorius longus muscle may be present and may be the cause of the tibial nerve compression.