The obturator internus makes a 90-degree turn around the lesser sciatic notch (using the bone as a pulley), emerging from the pelvis through the lesser sciatic foramen. An ischiofemoral bursa between the tendon and the notch reduces friction at this pulley point. Deep gluteal syndrome (previously called piriformis syndrome) often involves the obturator internus tendon in the deep gluteal space.
| Origin | Internal surface of the obturator membrane and adjacent pelvis — fills the obturator foramen from within the pelvis |
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| Insertion | Medial surface of the greater trochanter — the tendon bends 90 degrees around the lesser sciatic notch (using the ischium as a pulley) |
| Nerve Supply | Nerve to obturator internus (L5, S1) — from the sacral plexus |
| Blood Supply | Internal pudendal artery |
| Actions | Hip external rotation (when the hip is in neutral or extension); Hip abduction when the hip is flexed beyond 90 degrees (the line of pull shifts above the hip centre) |
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Deep gluteal syndrome from obturator internus tendinopathy produces posterior hip pain in the deep gluteal space, reproduced by the FAIR test and resisted hip external rotation. MRI with gadolinium identifies the tendon changes and any adjacent sciatic nerve signal. Ultrasound-guided injection at the lesser sciatic notch provides targeted treatment.
The obturator internus is palpable internally on rectal or vaginal examination as the lateral pelvic wall muscle, and externally by deep gluteal palpation at the ischial tuberosity level.
Deep gluteal space tendon pathology producing posterior hip pain managed with FAIR stretching and ultrasound-guided injection.
