An unusual cause of sciatic pain as a result of the dynamic motion of the obturator internus muscle

BACKGROUND CONTEXT: It has been reported that compression of the sciatic nerve because of any cause, including endometriosis, piriformis syndrome, abscess, tumor, adjoining uterus provoke sciatic pain. Some of these pathophysiologies have been diagnosed clinically and sometimes by exclusion. PURPOSE: To discuss the clinical features of sciatic neuropathy under the belief that dynamic motion of the obturator internus muscle and tendon should be included in the differential diagnosis of sciatic neuropathy. STUDY DESIGN: Sciatic neuropathy, which was because of compression of the sciatic nerve caused by dynamic motion of the tendon and muscle of the obturator internus, was reported. METHODS: We performed surgery to confirm the outlet of the pelvis. RESULTS: Although no compression was provoked by the piriformis muscle, obvious compression was observed on the sciatic nerve by the stretched obturator internus muscle. CONCLUSIONS: Although it may not be common, compression of the sacral plexus caused by dynamic motion of the obturator internus muscle should be included as a possible diagnosis for sciatic pain.