Anatomical Description of the Sciatic Nerve
The correct answer is E: The sciatic nerve supplies adductor magnus. 1
Anatomical Course and Relations
The sciatic nerve exits the pelvis through the greater sciatic foramen, typically passing below (inferior to) the piriformis muscle in approximately 92.5% of cases. 2, 3 It does not lie between piriformis and gluteus minimus (option A is incorrect).
Key Anatomical Relationships
After exiting the pelvis, the sciatic nerve descends between the greater trochanter of the femur and the ischial tuberosity, not on the posterior surface of the ischium itself (option C is incorrect). 4, 3
The nerve courses through the posterior thigh where it lies anterior to (on) the adductor magnus muscle in the upper thigh, along with quadratus femoris in the gluteal region. 1 However, option B's phrasing is imprecise as the primary relationship is more complex than simply "lying on" these structures.
The sciatic nerve does not have branches entering the pelvis via the lesser sciatic foramen (option D is incorrect). 2 The nerve exits (not enters) the pelvis via the greater sciatic foramen.
Motor Innervation Pattern
The sciatic nerve provides motor innervation to the adductor magnus muscle, specifically through branches from its tibial component. 1 This is a well-established anatomical fact that makes option E correct.
Additional Motor Supply
The sciatic nerve's motor branches supply:
Anatomical Variations to Consider
Common variations include the sciatic nerve dividing at different levels:
- Within the pelvis: 6% of cases 5
- In the gluteal region: 35% of cases 3
- Proximal popliteal fossa: 55% of cases 3
- Middle third of thigh: 10% of cases 3
The relationship to piriformis can vary, with the nerve occasionally passing through or above the muscle rather than below it in approximately 7.5% of cases. 3