A bilateral case of a long flexor accessorius muscle of the foot

Anomalies of the calf muscles are rare. One such anomalous muscle, known as the flexor accessorius longus muscle (also named accessorius ad accessorium, accessorius secondus, accessory flexor digitorum longus or pronator pedis) is of morphological significance. When present, this originates in the deep fascia those of either the tibia or fibula and inserts into the foot either into the flexor digitorum accessorius or into the tendons of the flexor digitorum longus. In this report we present a discussion of the morphological significance and phylogenetic history of one such muscle.