Sonographic anatomy and dynamic study of the normal iliopsoas musculotendinous junction.

The objective of the study was to document the anatomy of the iliopsoas muscle at the level of the groin with the use of sonography. At the same time, behaviour of the muscle during external rotation-flexion and abduction was dynamically evaluated. Forty-two hips in 21 asymptomatic volunteers were studied in static and dynamic conditions. Four bundles of the iliopsoas muscle were identified in all patients. A fifth one was found in only two hips. During dynamic study, a snap was explained by the sudden release of the most medial fibres of the ilacus from an entrapment between the tendon and the superior pubic ramus in 40% of our asymptomatic hips. Anatomy of the iliopsoas muscle can be accurately depicted by sonography at the level of the groin. Snapping of the muscle is often encountered as a physiological finding.