Posterior Hip Muscles
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Muscles of the Posterior Hip
- These muscles act on the thigh; they are innervated by the lumbosacral plexus.
Overview of the Posterior Pelvic Girdle & Ligaments
Review Pelvic Girdle:
- Iliac crest, superiorly
- Ischial spine
- Ischial tuberosity, inferiorly
- Gluteal lines serve as attachment points for the gluteal muscles: Posterior, Anterior, and Inferior.
Key Connective Tissues & Ligaments:
- Obturator membrane covers the obturator foramen.
- The obturator canal is a small opening in the membrane. The obturator nerve travels through this canal from the pelvic cavity to the anterior/medial thigh.
- These two ligaments serve as important landmarks and muscle attachment sites.
- Interosseous sacro-iliac ligament (deep): as its name suggests, it secures the sacrum and ilium.
- Posterior sacro-iliac ligament: a larger, more superficial ligament with fibers that run in multiple directions to secure the pelvic bones.
- Sacro-spinous ligament - runs from the sacrum to the ischial spine.
- Sacro-tuberous ligament - runs from the sacrum to the ischial tuberosity.
- Sciatic notch
- The interosseous sacroiliac and posterior sacroiliac ligaments pass over the sciatic notch, converting it into foramina:
Muscles of the Posterior Hip
Superficial muscles (gluteal muscles and tensor fascia latae) & deep (lateral rotators)
Superficial Muscles
- Gluteus minimus: the smallest and deepest of the gluteal muscles.
- Arises from the ilium, between the anterior and inferior gluteal lines, and inserts on the greater trochanter of the femur.
- Gluteus medius:
- Arises superior to gluteus minimus, between the anterior and posterior gluteal lines, and also inserts on the greater trochanter of the femur.
Notice that the fibers of gluteus medius and minimus run in similar directions; this helps us to remember that both act as abductors and medial rotators of the thigh.
- Tensor fascia latae: a small muscle that arises from the iliac crest and anterior superior iliac spine; this muscle is also visible in anterior and lateral views.
- The fascia that covers this muscle extends inferiorly as the iliotibial band, which attaches to the tibia (not shown); thus, the iliotibial band, aka, the IT band or tract, stabilizes the knee.
- Gluteus maximus: the largest muscle in the hip
- Arises from the posterior ilium and sacrum (specifically, from the sacro-tuberous ligament) and extends inferiorly and laterally; the deeper fibers of this thick muscle attach to the gluteal tuberosity of the femur, whereas the more superficial and anterior fibers attach along the iliotibial band.
Deep Muscles
- Quadratus femoris
- Arises from the ischial tuberosity and inserts on the intertrochanteric crest of the femur.
As its name suggests, this is a rectangular (“quadratic”) muscle; “femoris” refers to the femur – be careful not to confuse this muscle with rectus femoris, a long muscle in the anterior thigh.
- Inferior gemellus
- Arises from the ischial tuberosity and inserts on the greater trochanter of the femur.
- Obturator internus
- Arises from the obturator membrane and the ischiopubic rami and inserts on the greater trochanter via a thin tendon.
- Superior gemellus
- Arises from the ischial spine and inserts on the greater trochanter.
The gemelli and obturator internus muscles are so closely related in structure and function that they are sometimes referred to as the “triceps coxae.”
Be aware that fibers of the gemelli muscles also insert along the obturator internus tendon, so that the three muscles form a collective attachment.
- Piriformis
- A flat, broader muscle that arises from the anterior surface of the sacrum and passes through the greater sciatic foramen to attach on the greater trochanter of the femur.
- For context, we show gluteus minimus to see its relationship to these rotators.
- The sciatic nerve exits the pelvis via the greater sciatic foramen, travels deep to piriformis, then over the rest of the lateral rotators to the thigh.
- This anatomical relationship can be problematic, as the piriformis muscle can irritate or compress the sciatic nerve, resulting in piriformis syndrome, which is characterized by pain, tingling, or numbness along the posterior leg and into the foot.
- Intermuscular injections are given in the gluteal muscles in the superior lateral quadrant of the hip to avoid the sciatic nerve.
Sciatic Foramina & Contents
The greater sciatic foramen* is divided into superior and inferior portions by the piriformis muscle.
- Above the piriformis: the superior gluteal vessels and nerve travel to the glutes.
- Below the piriformis, several neurovascular structures pass: sciatic nerve, inferior gluteal vessels and nerve, internal pudendal vessels and nerve, posterior femoral cutaneous nerve and the nerve to obturator internus & superior gemellus muscles, and, the nerve to quadratus femoris and inferior gemellus muscles.