Muscles
The short external rotators are:
- Piriformis
- Superior gemellus
- Obturator internus
- Inferior gemellus
- Obturator externus
- Quadratus femoris
Piriformis
- Origin: anterior sacrum and margin of the greater sciatic notch
- Insertion: superior border of the greater trochanter
- Action: external rotation; assists abduction when the hip is flexed
- Innervation: nerve to piriformis, L5–S2
Obturator internus and gemelli
The obturator internus tendon passes through the lesser sciatic foramen and inserts on the medial aspect of the greater trochanter. Superior and inferior gemelli accompany its tendon.
- Superior gemellus is supplied by the nerve to obturator internus.
- Inferior gemellus is supplied by the nerve to quadratus femoris.
Obturator externus
- Origin: external surface of the obturator membrane and surrounding bone
- Insertion: trochanteric fossa
- Action: external rotation and adduction
- Innervation: posterior division of the obturator nerve
Quadratus femoris
- Origin: lateral ischial tuberosity
- Insertion: quadrate tubercle / intertrochanteric crest
- Action: external rotation and adduction
- Innervation: nerve to quadratus femoris, L4–S1 predominantly L5–S1
Surgical relevance
In the posterior approach to the hip, the piriformis and obturator internus complex are commonly detached close to the femoral insertion and reflected posteriorly. This helps protect the sciatic nerve. Repair of the posterior capsule and short external rotators at closure contributes to stability.
Relationship to the sciatic nerve
The sciatic nerve normally passes deep to the piriformis and then lies posterior to the short external rotators, including the quadratus femoris.
References
- Orthobullets — Hip posterior approach
- Orthobullets — Hip anatomy