Human Anatomy
Gluteal Region and Back of the Thigh
Gluteal region and back of thigh anatomy for MBBS: gluteal muscles, sciatic nerve, hamstrings, Trendelenburg sign and injection site, mapped to NMC codes AN16.1 to AN16.6.
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Gluteal Region and Back of the Thigh
Gluteal region and back of thigh anatomy for MBBS: gluteal muscles, sciatic nerve, hamstrings, Trendelenburg sign and injection site, mapped to NMC codes AN16.1 to AN16.6.
This chapter covers the gluteal region and the back of the thigh, dominated by the sciatic nerve and the muscles of hip extension. It links the gluteal muscles and their nerves to the Trendelenburg sign and the safe injection site, and covers the hamstrings and the course of the sciatic nerve.
High-yield: Gluteal Region and Back of the Thigh
- Gluteus maximus is the largest muscle of the region and is the chief extensor and lateral rotator of the hip.
- Gluteus medius and minimus abduct and medially rotate the hip and steady the pelvis during walking.
- Weakness of gluteus medius, as in a superior gluteal nerve lesion, causes the Trendelenburg sign with pelvic drop on the opposite side.
- The piriformis is the key to the gluteal region because structures leave the pelvis above or below it.
- The superior gluteal nerve and vessels leave above piriformis; most other structures leave below it.
- The sciatic nerve usually emerges below piriformis and descends midway between the ischial tuberosity and the greater trochanter.
- The safe site for intramuscular injection is the upper outer quadrant of the buttock, to avoid the sciatic nerve.
- The superior gluteal nerve supplies gluteus medius, gluteus minimus and tensor fasciae latae.
- The inferior gluteal nerve supplies gluteus maximus.
- The pudendal nerve and internal pudendal vessels leave below piriformis, cross the ischial spine and re-enter the perineum.
- The hamstrings are semitendinosus, semimembranosus and the long head of biceps femoris, supplied by the tibial part of the sciatic nerve.
- The short head of biceps femoris is supplied by the common peroneal part of the sciatic nerve.
- The hamstrings extend the hip and flex the knee and arise from the ischial tuberosity.
- The sciatic nerve divides into the tibial and common peroneal nerves usually at the upper part of the popliteal fossa.
Gluteal nerves and their muscles
- **Superior gluteal nerve:** Leaves above piriformis; supplies gluteus medius, minimus and tensor fasciae latae; injury gives Trendelenburg sign.
- **Inferior gluteal nerve:** Leaves below piriformis; supplies gluteus maximus.
- **Sciatic nerve:** Leaves below piriformis; supplies the hamstrings and, through its branches, the whole leg and foot.
- **Piriformis:** Key landmark; structures exit the greater sciatic foramen above or below it.
NMC competencies in this chapter
- **AN16.1:** Muscles of the gluteal region and their nerve supply
- **AN16.2:** Structures passing through the greater and lesser sciatic foramina
- **AN16.3:** Course and relations of the sciatic nerve
- **AN16.4:** Muscles of the back of the thigh (hamstrings)
- **AN16.5:** Nerves and vessels of the gluteal region and back of thigh
- **AN16.6:** Applied anatomy including intramuscular injection and Trendelenburg sign
Frequently Asked Questions
What is the Trendelenburg sign?
When gluteus medius and minimus are weak, they cannot steady the pelvis while standing on that leg, so the pelvis drops on the opposite side. This is the Trendelenburg sign and points to a superior gluteal nerve lesion.
Why is the upper outer quadrant used for injections?
Intramuscular injections into the buttock are given in the upper outer quadrant to keep well away from the sciatic nerve, which runs through the lower medial part of the region.
What is the relation of structures to piriformis?
Piriformis is the landmark of the gluteal region. The superior gluteal nerve and vessels leave above it, while the sciatic nerve, inferior gluteal and pudendal nerves and vessels leave below it.
Which muscles make up the hamstrings?
The hamstrings are semitendinosus, semimembranosus and the long head of biceps femoris, all supplied by the tibial part of the sciatic nerve. They extend the hip and flex the knee.
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