An accessory flexor of the fifth toe.

The presence of accessory muscles and other organs on the lower limbs of some individuals have variously been reported in the literature. We report an unusual muscle located on the plantar surface of the left foot of a cadaver, which had not been previously described. This muscle originated from the tendon of tibialis posterior and inserted into the middle phalanx of the fifth toe. It differed from the 'expansions' of the tibialis posterior tendon, which usually pass from its insertion on the navicular bone to other tarsal bones and are ligamentous in nature. The muscle produced flexion of the fifth toe and is innervated by the medial plantar nerve. Awareness of this is important to Anatomists and surgeons, especially those working on the foot.