Obturator Nerve: Course, Branches and Clinical Anatomy

By Dr Richard Miller, MBChB FRCS · Reviewed 1 October 2026

The obturator nerve is a branch of the lumbar plexus that runs along the side wall of the pelvis and through the obturator canal into the medial thigh. It arises from L2–L4, splits into anterior and posterior divisions around adductor brevis, and supplies the adductor muscles, the skin of the medial thigh, and the hip and knee joints.

Obturator Nerve · key facts

Roots: L2–L4, anterior divisions of the ventral rami
Course: Medial border of psoas, lateral pelvic wall, obturator canal, medial thigh
Motor supply: Obturator externus, adductor longus, brevis and magnus (adductor part), gracilis; sometimes pectineus
Sensory supply: Variable patch of skin on the medial thigh
Branches: Anterior and posterior divisions; articular branches to hip and knee
Key relations: Above the obturator vessels in the canal; divisions either side of adductor brevis
Injury: Weak adduction, wide-based gait, medial thigh numbness

Course

The obturator nerve runs from inside psoas major, down the lateral wall of the true pelvis and out through the obturator canal into the adductor compartment of the thigh.

In the abdomen and pelvis

It forms within psoas major from the anterior divisions of L2, L3 and L4, and it is the main branch to emerge from the medial border of the muscle. It passes behind the common iliac vessels at the pelvic brim, lateral to the internal iliac vessels, then runs forward and down on obturator internus in the side wall of the pelvis. On this wall it lies above the obturator artery and vein In the female it forms part of the lateral wall of the ovarian fossa, so ovarian disease can refer pain to the medial thigh.

Through the obturator canal

The obturator canal is the gap at the top of the obturator foramen where the obturator membrane falls short of the superior pubic ramus. The nerve is the uppermost structure in the canal, with the obturator vessels below it. It divides into anterior and posterior divisions in or just beyond the canal.

In the thigh

The two divisions straddle adductor brevis. The anterior division runs in front of obturator externus and adductor brevis, behind pectineus and adductor longus. The posterior division pierces obturator externus and descends behind adductor brevis, in front of adductor magnus.

Branches and distribution

The obturator nerve supplies the muscles of the medial compartment of the thigh, apart from the hamstring part of adductor magnus and usually pectineus.

Division	Muscles	Cutaneous	Articular
Anterior	Adductor longus, adductor brevis, gracilis; occasionally pectineus	Skin of the medial thigh, via a branch that emerges between gracilis and adductor longus	Hip joint
Posterior	Obturator externus, adductor part of adductor magnus; sometimes adductor brevis	None	Knee joint, via a twig that follows the popliteal artery

Adductor magnus has a double supply: its adductor part from the obturator nerve and its hamstring (ischiocondylar) part from the tibial part of the sciatic nerve. The anterior division also contributes to the subsartorial plexus, a network of fine nerves under sartorius shared with the saphenous nerve and the medial cutaneous nerve of thigh.

Accessory obturator nerve

An accessory obturator nerve (L3, L4) is present in a minority of people. It runs along the medial border of psoas, crosses over the superior pubic ramus rather than through the canal, and supplies pectineus and the hip joint.

Relations

The most important relations of the obturator nerve are on the lateral pelvic wall, where it is exposed during pelvic surgery.

Posterior abdominal wall: medial border of psoas major, next to the lumbosacral trunk, which lies deeper and lower.
Pelvic wall: obturator internus laterally, the external iliac vessels above, the obturator lymph nodes around it, and the ureter and internal iliac vessels medially.
Obturator canal: the obturator artery and vein lie below the nerve.
Thigh: adductor brevis separates the two divisions; pectineus and adductor longus lie in front, adductor magnus behind.

Clinical relevance

Obturator nerve injury weakens hip adduction and numbs a patch of the medial thigh; isolated lesions are uncommon because the nerve is well protected in the pelvis.

Causes

Pelvic surgery: pelvic lymph node dissection for gynaecological, bladder and prostate cancer clears the obturator fossa around the nerve.
Pelvic fractures and hip arthroplasty with deep acetabular screws or retractors.
Childbirth: compression of the nerve against the pelvic wall by the fetal head or forceps.
Obturator hernia: a rare hernia through the obturator canal, typically in thin older women. Compression of the nerve gives pain along the medial thigh to the knee (the Howship–Romberg sign).

Signs

The patient has weak adduction and an outward swinging, wide-based gait. Sensory loss is small and variable.

Referred pain

Because the obturator nerve supplies both the hip and the knee, hip disease often presents as knee pain, particularly in children with slipped capital femoral epiphysis or Perthes disease. Examine the hip in any child with knee pain.

Obturator nerve reflex

The nerve lies just outside the lateral bladder wall. During transurethral resection of a lateral wall tumour, the diathermy current can stimulate it and make the thigh adduct suddenly, risking bladder perforation. An obturator nerve block prevents this.

How it is examined

On a cadaveric spotter, in an OSPE and in MRCS Part B anatomy.

On a pelvic side-wall prosection, the nerve running forward on obturator internus toward the top of the obturator foramen, above the obturator vessels, is the obturator nerve.
In the medial thigh, a pin on a nerve lying on the front of adductor brevis, behind adductor longus, is the anterior division of the obturator nerve. The branch behind adductor brevis is the posterior division.
Look-alike: the femoral nerve emerges from the lateral border of psoas; the obturator nerve emerges from the medial border. Expect this as a viva question.
Classic follow-up: why hip disease refers pain to the knee (shared obturator supply) and which muscle has a double nerve supply (adductor magnus).
Be ready to name the sign of an obturator hernia (Howship–Romberg) and the urological reason to block this nerve (adductor jerk during TURBT).

Key points

The obturator nerve arises from the anterior divisions of L2–L4 and emerges from the medial border of psoas.
It runs on the lateral pelvic wall and leaves through the obturator canal, above the obturator vessels.
Its anterior and posterior divisions straddle adductor brevis.
It supplies the adductors, gracilis, obturator externus and a variable patch of medial thigh skin.
Its supply to both hip and knee explains hip pain referred to the knee.

Common questions

What does the obturator nerve supply?

The obturator nerve supplies the adductor compartment of the thigh: adductor longus, adductor brevis, the adductor part of adductor magnus, gracilis and obturator externus, and occasionally pectineus. It gives a cutaneous branch to a variable area of skin on the medial thigh and articular branches to both the hip and knee joints. Its main job is adduction of the thigh at the hip.

Where does the obturator nerve leave the pelvis?

The obturator nerve leaves the pelvis through the obturator canal, a short passage at the top of the obturator foramen between the obturator membrane and the groove on the underside of the superior pubic ramus. The obturator artery and vein travel with it, lying below the nerve. Once through the canal, the nerve divides into anterior and posterior divisions in the medial thigh.

What are the symptoms of obturator nerve damage?

Obturator nerve damage weakens adduction of the thigh, so the leg swings outward when walking and the gait becomes wide-based. Many patients describe pain or numbness along the inner thigh, sometimes reaching the knee. Isolated injury is uncommon and usually follows pelvic surgery, pelvic fracture or a difficult delivery. Pain along the medial thigh can also be the only sign of an obturator hernia.

Why can hip problems cause knee pain?

Hip problems cause knee pain because the obturator nerve, and to a lesser extent the femoral nerve, supplies both joints. Pain signals from the hip travel in the same nerve as sensation from the knee and medial thigh, so the brain misplaces the source. This is why a child with slipped capital femoral epiphysis may present with knee pain and a normal knee examination.

References

Gray's Anatomy: The Anatomical Basis of Clinical Practice. Standring S (ed). Elsevier. 42nd edition, 2020.
Moore's Clinically Oriented Anatomy. Moore KL, Dalley AF, Agur AMR. Wolters Kluwer. 9th edition, 2022.
Last's Anatomy: Regional and Applied. Elsevier.