Muscles Supplied by the Sciatic Nerve
The sciatic nerve supplies all muscles in the posterior thigh (hamstring group) and all muscles below the knee through its terminal branches.
Hamstring Muscles (Posterior Thigh)
The sciatic nerve directly innervates the hamstring muscle group in the posterior compartment of the thigh 1:
- Biceps femoris (long head) - receives an average of 1.8 branches from the sciatic nerve, with 35% receiving 1 branch, 50% receiving 2 branches, and 15% receiving 3 branches 2
- Semitendinosus - receives an average of 1.5 branches, with 55% receiving 1 branch and 45% receiving 2 branches 2
- Semimembranosus - receives an average of 1.4 branches, with 60% receiving 1 branch and 40% receiving 2 branches 2
These branches typically originate from the anteromedial part of the sciatic nerve within 15 cm of the lateral surface of the greater trochanter (5 cm above to 10 cm below), with no branches emerging below the lower edge of the gluteus maximus muscle 2, 3.
Adductor Magnus (Partial Innervation)
- Adductor part of adductor magnus (AM3 region) - receives dual innervation from both the obturator nerve and the tibial portion of the sciatic nerve in 95.2% of cases 4
- The sciatic nerve supplies not only the traditional "hamstrings part" (AM4) but also extends into the adductor part more widely than traditionally believed 4
Muscles Below the Knee
Through its two terminal branches (tibial and common peroneal/fibular nerves), the sciatic nerve supplies 1:
- All muscles in the gluteal region (motor only) 1
- All muscles in the lateral and posterior thigh 1
- All muscles in the lower leg and foot via the peroneal and tibial nerve territories 1
Clinical Relevance
The sciatic nerve or its branches cross both the hip and the knee joints, making it vulnerable to stretch injury with excessive hip flexion or hamstring stretching 1. Positions that stretch the hamstring muscle group beyond comfortable range during preoperative assessment should be avoided to prevent sciatic nerve injury 1. The nerve's extensive distribution explains why sciatic neuropathy causes weakness and sensory loss in the gluteal (motor only), peroneal, and tibial nerve territories 1.