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The obturator nerve or nervus obturatorius in Latin arises from the ventral branches of the second to fourth anterior rami (L2- L4). The branch coming from the third is considered the largest, while the second is usually very small.
The obturator nerve descends in the psoas major, continues behind the common iliac vessels, and passes across the lateral wall of the pelvic cavity. It then enters the obturator canal, where it gains access to medial compartment of the thigh. Near the canal, it splits into anterior and posterior branches. They are separated at first by the obturator externus muscle and lower down by the adductor brevis.
The anterior branch exists the pelvis anterior to the obturator externus, goes downwards in front of the adductor brevis and behind both the pectineus and adductor longus. At the lower border of the adductor longus, the anterior branch communicates with the medial cutaneous and saphenous branches of the femoral nerve. This communication forms the subsartorial plexus present deep to the fascia lata; through it, the skin on the medial side of the thigh is supplied. It then descends to supply the femoral artery, and the hip joint. Posterior to the pectineus muscle, it supplies the adductor longus, gracilis, adductor brevis, and pectineus occasionally. It connects with the accessory obturator nerve if present (10% of people).
The posterior branch perforates the obturator externus, supplies it and proceeds to pass behind the adductor brevis towards the adductor magnus. It sends off an articular filament branch to the knee joint, where it enters the popliteal fossa. Here, it descends to the back of the knee on the popliteal artery, pierces the oblique posterior ligament, and supplies the articular capsule.
Isolated lesions of the obturator nerve are very rare. They can be a result of direct trauma, like in childbirth or hip dislocation. Nerve damage can also be attributed to other conditions including obturator hernias, retroperitoneal lesions, and entrapment in athletes with large adductor muscles. Injury to this nerve may cause painful spasms of the adductor muscles of the thigh and sensory deficits in the medial thigh region.
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