Obturator nerve is the largest nerve formed from the anterior divisions of lumbar plexus (L2,L3,L4).The roots unite within the posterior pa of psoas, and then descends through psoas and runs downward over sacral ala into lesser pelvis, lying lateral to ureter and internal iliac vessels. They enter the upper pa of the obturator foramen and then subsequently divides into anterior and posterior branches. Anterior Division:Muscular branches: To the following muscles;GracilisAdductor brevisAdductor longusPectineus (variable)Aicular branches: To hip jointSensory branches: To medial aspect of thigh Posterior Division:Muscular branches: To the following muscles;Obturator externusAdductor pa of adductor magnusAdductor brevis (variable)Aicular branch: To knee joint Must know:Adductor magnus has double nerve supply. Its adductor pa is supplied by the obturator nerve, while its hamstring pa is supplied by the tibial pa of the sciatic nerve. The pectineus also has a double innervation; its anterior fibres are supplied by the femoral nerve and the posterior fibres by the obturator nerve.