The biceps femoris muscle is the largest and most lateral of the caudal muscles of the thigh. It is superficial, covered only by the fascia and skin. It consists of a strong cranial part (vertebral head) which arises for the sacrum and the sacrotuberous ligament and a smaller caudal part (vertebral head), which arises from the ischium. These parts are not listed in the VIth NAV, but:
Both muscle bellies broaden distally and unite by means of an aponeurosis with the crural fascia and fascia of the stifle. Though this fascia, the biceps femoris insert to the patella, the patellar ligament and the tibial tuberosity. A distinct distal tendon of the main musclepasses distally under the abductor muscle of the thigh and along the gastrocnemius muscle. It curves in front of the main part of the calcaneal tendon ot insert on the calcaneal tuber after cominbint with a similar tendon form the semitendinous muscle.
Origin: Ventrocaudal end of the sacrotuberous ligament, lateral angle of the ischial tuberosity.
Insertion: Tibial tuberosity, tibial crest, medial tuberosity of the tuber calcanei via the calcaneal tendon.
Action: Antigravity in stance phase of locomotion, knee flexion at the start of the swing phase of locomotion and tarsal joint extension.
Nerve: Ischiadicus and ramus distalis of the gluteus caudalis nerve.