The long accessory flexor muscle: an anatomical study.

A total of 136 lower limbs from 68 human cadavers were dissected to determine the incidence of the long accessory flexor muscle and its origins and insertions. The muscle was present in 11 of 136 lower extremities (8%) and 9 of 68 cadavers (13%). Five long accessory flexor muscles originated from the tibia and fascia of the deep posterior compartment and six began on the fibula. All of the tendons were deep to the laciniate ligament and coursed within the tarsal tunnel. All five of the tendons originating from the tibia inserted on the quadratus plantae, with two of the tendons having an additional insertion on the flexor digitorum longus. Three of the tendons with fibular origin inserted on the quadratus plantae and three inserted on the flexor digitorum longus. The importance of the long accessory flexor muscle relates as a cause or association with tarsal tunnel.