Obturator Internus Muscle

Description

Running along the internal surface of the obturator foramen, the obturator internus forms a broad muscular sheet on the pelvic side of the obturator membrane and adjacent pubis and ischium in an adult male. Its fibers converge posteriorly into a tendon that turns sharply through the lesser sciatic foramen, where the muscle belly lies medial to the acetabulum while the tendon courses posterior to the hip joint to reach the medial surface of the greater trochanter. Lateral to the tendon, the femoral head seats within the acetabulum, and the hip capsule and labrum outline the joint margins. Depth and direction matter. Clinically, this anatomy explains the pulley-like function of obturator internus as an external rotator of the extended hip and an abductor of the flexed hip, acting in concert with gemellus superior and inferior at the level of the ischial spine and ischial tuberosity. The tendon’s close relationship to the posterior capsule makes it relevant in posterior hip pain syndromes and in deep gluteal space disorders where obturator internus bursitis or tendinopathy can mimic intra-articular pathology. It also frames the operative corridor for posterior approaches to the hip, where short external rotators are released and later repaired to reduce dislocation risk. Pelvic anatomy and orthopaedic teaching benefit from this view when clarifying the difference between obturator internus (pelvic wall, tendon exiting the pelvis) and obturator externus (external surface, separate course), a common point of confusion in gross anatomy and radiology correlation sessions. The illustration also supports surgical atlas content on hip arthroplasty, posterior dislocation mechanisms, and targeted injection planning for suspected obturator internus tendinobursitis. Anatomical accuracy verified by SciePro's Medical Advisory Board.