ABSTRACT
Anomalies of the calf muscles are rare. One such anomalous muscle, known as the Muscle
Flexor accessorius longus (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 of the tibia or fibula and inserts
in 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 observed. In this case report
we describe an anomalous calf muscle which extends from the popliteal region, runs
along the posterior compartment of the leg, reaches the sole and is inserted to the
flexor digitorum longus muscle. This kind of muscle variations are considered to be
the higher origin of the flexor digitorum accessorius muscle of the sole. Here we
discuss the phylogenetic history of this muscle as this muscle variant is present
in some primitive mammals, absent in apes and in this particular case appeared as
one of the muscles of the flexor compartment of the leg.
KEY WORDS
Flexor accessorius longus - flexor digitorum accessorius - foot - muscular variations
