An accessory flexor digitorum longus muscle.

An accessory flexor digitorum longus muscle (M. flexor digitorum longus accessorius) in a 60-year-old male cadaver was encountered during routine dissections in our laboratory. The muscle originated from the deep transverse fascia of the leg, covering flexor digitorum longus, flexor hallucis longus, and tibialis posterior muscles, and additionally from some fibres of these muscles. After the tendon of the muscle passed behind the medial malleolus, it inserted into the tendon of the flexor digitorum longus muscle where the latter separated into four digital tendons.