Obturator nerve
Nervus obturatorius
The nerve of the medial (adductor) compartment of the thigh (L2–L4, anterior divisions). It runs along the lateral pelvic wall and through the obturator canal to supply the hip adductors and a patch of skin on the medial thigh.
Overview
The obturator nerve is the only major branch of the lumbar plexus to emerge from the medial border of psoas. It crosses the pelvic brim behind the common iliac vessels and descends on the lateral pelvic wall on the fascia of obturator internus, in front of the internal iliac vessels and ureter. It leaves the pelvis through the obturator canal, in the upper part of the obturator foramen, with the obturator vessels.
In the thigh it divides around adductor brevis:
• the anterior division passes in front of adductor brevis and behind pectineus and adductor longus; it supplies adductor longus, adductor brevis, gracilis and often pectineus, the hip joint and a variable area of medial thigh skin;
• the posterior division passes behind adductor brevis and supplies obturator externus and the adductor part of adductor magnus; it also sends an articular branch to the knee.
Because one nerve supplies both the hip and knee joints, hip disease (for example in children) often presents as knee pain (Hilton's law).
- Location
Medial border of psoas → lateral pelvic wall → obturator canal → medial thigh.
Anatomy
- Innervation
- Motor: the hip adductors (adductor longus, brevis and magnus [adductor part]), gracilis and obturator externus, ± pectineus.
• Sensory: the skin of the middle of the medial thigh, and the hip and knee joints.- Nerve roots
L2, L3, L4 (anterior divisions).
- Course
Medial border of psoas → behind the common iliac vessels, lateral to the internal iliac vessels and ureter → lateral pelvic wall (on obturator internus) → obturator canal (with the obturator vessels) → anterior and posterior divisions around adductor brevis.
- Branches
- Anterior division: adductor longus, adductor brevis, gracilis, (pectineus), hip joint, and the cutaneous branch to the medial thigh.
• Posterior division: obturator externus, adductor magnus (adductor part), (adductor brevis), and the knee joint.
Function
- Adduction of the thigh (crossing the legs, stabilising the pelvis in gait)
- Assists medial or lateral rotation and flexion of the hip
- Sensation of the medial thigh and the hip and knee joints
Clinical significance
Obturator nerve injury
It is injured in pelvic surgery (lymph node dissection for gynaecological or urological cancer), pelvic fractures, childbirth (compression by the fetal head or forceps) and by tumours on the lateral pelvic wall. The findings are weak adduction with a wide-based, circumducting gait and numbness of the medial thigh.
Obturator hernia and referred pain
An obturator hernia, classically in thin, elderly, multiparous women, compresses the nerve in the obturator canal. It causes pain along the medial thigh to the knee, which is worse with hip extension, adduction or medial rotation (Howship–Romberg sign). Inflammation of the ovary or a pelvic appendix touching the lateral pelvic wall can also refer pain to the medial thigh.
Compiled from standard anatomy and physiology references — see the Nervous System sources. For education only; not medical advice.