Must Know
- Gluteal region runs from the iliac crest to the gluteal fold, behind the pelvis and hip.
- Greater sciatic foramen is bounded by the greater sciatic notch, sacrotuberous and sacrospinous ligaments.
- Piriformis almost fills the greater sciatic foramen and organises every other structure in the buttock.
- Only the superior gluteal nerve and vessels pass above piriformis.
- Inferior gluteal, pudendal, sciatic and posterior femoral cutaneous nerves pass below piriformis.
- Nerves to obturator internus and quadratus femoris and the internal pudendal vessels also pass below.
- Superior gluteal nerve (L4, L5, S1) runs between gluteus medius and minimus and ends in tensor fasciae latae.
- Inferior gluteal nerve (L5, S1, S2) supplies gluteus maximus only.
- Neither gluteal nerve has a cutaneous branch.
- Gluteus maximus inserts three quarters into the iliotibial tract and one quarter into the gluteal tuberosity.
Nerves Leaving Below Piriformis
| Nerve | Roots | Course and supply |
|---|---|---|
| Sciatic | L4 to S3 | Most lateral, on ischium and posterior acetabulum, over obturator internus and quadratus femoris |
| Posterior femoral cutaneous | S1 to S3 | On the sciatic nerve, then down the back of thigh to midcalf |
| Pudendal | S2 to S4 | Over sacrospinous ligament medial to ischial spine, out through lesser sciatic foramen |
| Nerve to obturator internus | L5, S1, S2 | Loops around ischial spine base. Also supplies superior gemellus |
| Nerve to quadratus femoris | L4, L5, S1 | Deep to sciatic nerve, gives hip branch. Also supplies inferior gemellus |
| Inferior gluteal | L5, S1, S2 | Into deep surface of gluteus maximus |
- Internal pudendal artery crosses the tip of the ischial spine lateral to the pudendal nerve.
- Nerve to obturator internus lies most laterally of the three around the ischial spine.
- Piriformis is supplied directly by S1 and S2 anterior rami.
- Posterior femoral cutaneous nerve shares S2 and S3 with pelvic parasympathetics, so pelvic pain can refer to the posterior thigh.
Sciatic Nerve in the Buttock
- Enters the buttock one third of the way from ischial tuberosity to posterior superior iliac spine.
- Lies just medial to the midpoint between greater trochanter and ischial tuberosity.
- Obturator internus and gemelli separate it from the hip capsule.
- High division may let the components leave the pelvis separately.
- In a high division the common peroneal part pierces piriformis and the tibial part passes below.
- Misplaced gluteal injection is the commonest cause of sciatic injury.
- Safe injection site is the upper outer quadrant of the true buttock, crest to gluteal fold.
Short External Rotators
| Muscle | Origin | Insertion | Nerve |
|---|---|---|---|
| Piriformis | Front of middle three sacral pieces | Upper border of greater trochanter | S1, S2 |
| Obturator internus | Inner pelvic wall, turning at lesser sciatic notch | Medial greater trochanter above trochanteric fossa | Nerve to obturator internus |
| Superior gemellus | Ischial spine | Obturator internus tendon | Nerve to obturator internus |
| Inferior gemellus | Ischial tuberosity | Obturator internus tendon | Nerve to quadratus femoris |
| Quadratus femoris | Ischial tuberosity | Quadrate tubercle | Nerve to quadratus femoris |
| Obturator externus | Obturator membrane and margin | Trochanteric fossa | Obturator, posterior division |
- These muscles laterally rotate the extended hip and abduct the flexed hip.
- Quadratus femoris lies edge to edge with inferior gemellus above and adductor magnus below.
More on vessels of the buttock
- Superior gluteal artery has a superficial branch to gluteus maximus and a deep branch between medius and minimus.
- Inferior gluteal artery emerges between piriformis and superior gemellus and gives the artery to the sciatic nerve.
- Trochanteric anastomosis lies near the trochanteric fossa and feeds the femoral head through retinacular vessels.
- Cruciate anastomosis lies at the lesser trochanter level, joining both circumflex arteries, first perforator and inferior gluteal artery.
- Medial circumflex femoral artery passes between quadratus femoris and adductor magnus to the cruciate anastomosis.
Gluteal Function and Gait
- Gluteus medius and minimus abduct the hip and their anterior fibres medially rotate it.
- Stance side abductors stop the pelvis sagging toward the lifted leg.
- Positive Trendelenburg test is a fall of the unsupported side of the pelvis.
- Abductor paralysis gives a lurch of the trunk toward the stance limb.
- Gluteus maximus works at the extremes of extension, climbing stairs and rising from sitting.
- Hamstrings are the main hip extensors in quiet walking.
Numbers to Remember
- Sciatic entry point. One third of the way from ischial tuberosity to posterior superior iliac spine.
- Gluteus maximus. Three quarters into iliotibial tract.
- Sciatic injury after hip dislocation. About 7 percent, rising to 16 percent with fracture dislocation.
Memory Aids
- One above, many below. Only superior gluteal structures pass above piriformis.
- Pudendal goes out and back in. Out through the greater foramen, back in through the lesser foramen.
- Gemelli follow their neighbour. Superior with obturator internus nerve, inferior with quadratus femoris nerve.
Exam Traps
- Tensor fasciae latae takes the superior gluteal nerve, not the inferior.
- In a high division it is the common peroneal component that pierces piriformis.
- The gluteal fold is the hip skin crease, not the lower border of gluteus maximus.
- Skin of the buttock skips the L2 to S2 segments, which lie out in the limb.
Source
Sinnatamby CS. Last’s Anatomy. Regional and Applied. 12th ed. Edinburgh, Churchill Livingstone Elsevier, 2011. Chapter 3, Lower limb. p. 111-78.
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 17 October 2026.