The Anatomy of the Obturator Nerve

The obturator nerve is a major peripheral nerve in your thigh. It's responsible for some leg movements (motor function) as well as sensation (sensory function).

This nerve is formed by portions of the lumbar plexus, which is a complex network of nerves that emerge from the lumbar region of the spine, which is in your lower back.

Anatomy

Your spinal nerves emerge from the spinal cord, then travel between your vertebrae to get to the rest of your body.

The lumbar region of the spine is in the abdominal region of your torso, and the roots of the obturator nerve come from the second, third, and fourth lumbar vertebrae.

Peripheral nerves are those that serve your limbs.

Structure

Nerves are structured like tree branches, with large branches splitting off into smaller divisions. This allows them to reach all the different structures in your body that they innervate (supply nerve function to).

The obturator nerve has three major branches:

1. Anterior (front) division
2. Posterior (rear) division
3. Cutaneous (skin) branch

Location

After its formation in the lumbar plexus, the obturator nerve travels down through the psoas major muscle, which runs diagonally from the mid-spine to the pelvic bone, and exits from the muscle's inner edge.

It then runs along the common iliac artery and across the pelvic wall. It then passes through an opening in the pelvic bone called the obturator foramen.

Inside the foramen, it enters the obturator canal, which carries it into the inner thigh compartment. There, the nerve divides into its anterior and posterior branches.

The anterior division continues its downward course toward the femoral artery, innervating these inner-thigh muscles:

• Adductor longus
• Adductor brevis
• Gracilis

The anterior division then pierces a connective tissue called the fascia lata, which is deep in the thigh. At that point, it becomes the cutaneous branch.

Meanwhile, the posterior division moves down through the obturator externus muscle, a fan-shaped muscle that runs from the neck of the femur (thigh bone) across the back of the pelvic bone. It then continues on and innervates two more inner thigh muscles:

• Part of the adductor magnus
• Obturator externus

Anatomical Variations

In rare cases, the anterior division of the obturator nerve provides motor function to the pectineus muscles, which is typically innervated by the femoral nerve.

Function

Because the obturator nerve supplies both motor and sensory function, it's considered a mixed nerve.

Motor

All of the muscles that get motor function from the obturator nerve—both anterior and posterior divisions—are involved in moving the thigh, mostly through adduction, which is moving a body part toward the midline of the body. In other words, pulling the leg in, such as when you bring your legs together during jumping jacks.

This includes the:

• Adductor longus
• Adductor brevis
• Part of the adductor magnus (its hamstring portion is innervated by the sciatic nerve)
• Gracilis

The obturator externus is the only non-adductor muscle innervated by the obturator nerve. This muscle is responsible for rotating the thigh outward.

Sensory

The cutaneous branch of the obturator nerve supplies sensation to the:

• Hip joint
• Knee joint
• Some of the skin over the adductor muscles in the inner thigh

The skin innervated by this branch is a small patch high up on the leg. The rest of the skin in that area is supplied by the anterior cutaneous branches of the femoral nerve.

Associated Conditions

Injury to the obturator nerve is somewhat rare because of how deep the nerve is buried in the thigh. However, an injury is possible and may be caused by:

• Abdominal or pelvic surgery
• Injury to the inner thigh
• Entrapment in the obturator canal
• Compression caused by pregnancy or pelvic tumors
• Trauma caused by childbirth
• Sports that involve a lot of running and/or twisting of the leg

Rehabilitation

If damage to the obturator nerve is mild, it can often be treated conservatively with physical therapy and anti-inflammatory medications.

However, if the damage is severe or symptoms persist, surgery may be necessary. It'll likely be followed by physical therapy as part of the rehabilitation plan.