📝 STANDARD DESCRIPTION:
3 Big muscles on caudal thigh:
1. Biceps Femoris — most LATERAL; from tuber ischiadicum & sacrum.
2. Semitendinosus — middle, longer & rope-like.
3. Semimembranosus — most MEDIAL; broader.
Common origin: Mostly from tuber ischiadicum (in ox, biceps also from sacrum → 'gluteobiceps').
Insertion: Patella + tibial crest + calcaneus (via crural fascia).
Function: Extend the hip; flex the stifle; extend the hock — essentially PROPEL the body forward.
Nerve: Tibial part of Sciatic nerve.
📚 DETAILED DESCRIPTION:
HAMSTRINGS — THE BACK-OF-THIGH POWER MUSCLES
The 'hamstring' group is three large muscles on the back of the thigh that work together to extend the hip (push off) and flex the stifle.
1. BICEPS FEMORIS: Most lateral. Has 2 heads (vertebral & ischial). In ox the cranial vertebral head fuses with the superficial gluteus = 'gluteobiceps'.
2. SEMITENDINOSUS: A long rope-like muscle in the middle. The visible 'string' on the caudal thigh of cattle.
3. SEMIMEMBRANOSUS: Most medial; broad and flat. Forms the medial outline of the back of the thigh.
ORIGIN: Mostly tuber ischiadicum (pin bone). Biceps femoris also from caudal sacrum (and ilium in ox).
INSERTIONS (the three muscles fan onto): Patella + lateral patellar ligament, tibial crest, calcaneus (via the crural fascia).
FUNCTIONS — combined:
• EXTEND the hip (powerful push-off).
• FLEX the stifle.
• EXTEND the hock (when foot is on ground).
• Together they are the engine of forward movement and kicking.
NERVE: Tibial portion of the SCIATIC nerve.
BUTCHER'S CUT: The 'silver-side' / 'topside' of beef = semimembranosus + semitendinosus.
// COMPARATIVE ANALYSIS
| HORSE |
Same 3 muscles, very powerful — drive the gallop. |
| DOG |
Same; well-developed; visible easily in lean dogs. |
CLINICAL RELEVANCE
Sciatic Nerve Injury: Damages tibial portion → hamstrings cannot contract → animal cannot extend hip or flex stifle properly.
Penetrating injuries of caudal thigh can damage hamstrings → severe lameness.
