Attachments
The gluteal muscles lie in three layers: gluteus maximus on the surface, gluteus medius in the middle, and gluteus minimus with piriformis and the short rotators deepest.
| Muscle | Origin | Insertion | Nerve | Main action |
|---|---|---|---|---|
| Gluteus maximus | Ilium behind the posterior gluteal line, back of the sacrum and coccyx, sacrotuberous ligament | Most into the iliotibial tract; deeper lower fibres into the gluteal tuberosity | Inferior gluteal (L5, S1, S2) | Extends and laterally rotates the hip |
| Gluteus medius | Outer ilium between the anterior and posterior gluteal lines | Lateral surface of the greater trochanter | Superior gluteal (L4, L5, S1) | Abducts the hip; anterior fibres rotate it medially |
| Gluteus minimus | Outer ilium between the anterior and inferior gluteal lines | Anterior surface of the greater trochanter | Superior gluteal (L4, L5, S1) | Abducts and medially rotates the hip |
| Piriformis | Front of the sacrum, inside the pelvis | Upper border of the greater trochanter | Nerve to piriformis (S1, S2) | Laterally rotates the extended hip |
| Obturator externus | Outer surface of the obturator membrane and surrounding bone | Trochanteric fossa | Obturator nerve (L3, L4) | Laterally rotates the hip |
Gluteus maximus is most active when the hip extends against resistance, as in climbing stairs or rising from a chair, and does little in level walking. Tensor fasciae latae, supplied by the superior gluteal nerve, joins medius and minimus as an abductor through the iliotibial tract.
Relations
Piriformis is the landmark of the gluteal region. It leaves the pelvis through the greater sciatic foramen, and every other structure passing through the foramen is described as above or below it: the superior gluteal nerve and vessels above; the inferior gluteal nerve and vessels, the sciatic nerve and the posterior cutaneous nerve of the thigh below.
The superior gluteal nerve runs forwards between gluteus medius and minimus, supplying both and ending in tensor fasciae latae. Obturator externus lies deepest of all, below the neck of the femur; its tendon passes under the neck to reach the trochanteric fossa, and it belongs with the adductors of the medial thigh by nerve supply.
Above the gluteal region, the posterior free border of external oblique reaches the iliac crest. With latissimus dorsi behind it and the iliac crest below, it forms the inferior lumbar triangle (of Petit), whose floor is internal oblique. External oblique arises from the lower eight ribs, inserts on the anterior half of the iliac crest and into its aponeurosis, and is supplied by the lower thoracic nerves (T7–T12).
Blood supply and innervation
The gluteal muscles are supplied by the two gluteal branches of the internal iliac artery. The superior gluteal artery, the largest branch of the internal iliac, emerges above piriformis and supplies medius, minimus and the upper part of maximus. The inferior gluteal artery emerges below piriformis and supplies the lower part of maximus. Both join the trochanteric and cruciate anastomoses around the upper femur.
The superior gluteal nerve (L4, L5, S1) and inferior gluteal nerve (L5, S1, S2) are branches of the sacral plexus and accompany the corresponding arteries.
Clinical relevance
Failure of the hip abductors is the most important clinical consequence of gluteal injury.
- Trendelenburg sign: when the patient stands on the affected leg, weak medius and minimus cannot hold the pelvis, and it drops on the opposite side. Causes include superior gluteal nerve injury, hip disease and a shortened lever arm after fracture or dislocation.
- Lateral approach to the hip: splitting gluteus medius too far above the greater trochanter risks the superior gluteal nerve, which runs a few centimetres above the tip.
- Intramuscular injection: given into the upper outer quadrant of the buttock (into medius), or the ventrogluteal site, to stay clear of the sciatic nerve.
- Greater trochanteric pain syndrome: tendinopathy or tears of the medius and minimus insertions, often with trochanteric bursitis, cause lateral hip pain lying on that side.
- Piriformis syndrome: buttock pain with sciatic symptoms attributed to compression of the nerve by piriformis; a debated diagnosis.
- Lumbar hernia: a rare hernia through the inferior lumbar triangle at the posterior border of external oblique.
On the specimen
The station shows the gluteal muscles layer by layer, with the abdominal wall above. Gluteus maximus is the thick, coarse-fibred sheet on the surface, running down and laterally. With it reflected, gluteus medius is the fan-shaped muscle under its upper part, and gluteus minimus lies deeper still, attached to the front of the greater trochanter.
Piriformis is the pear-shaped muscle running almost horizontally from the sacrum to the top of the trochanter, just below the lower border of minimus. Obturator externus is seen only from below and behind the femoral neck, its tendon passing to the trochanteric fossa. The muscle labelled above the iliac crest is external oblique, with its fibres running downwards and forwards.