The obturator nerve plays a role in both movement and sensation within the lower limb. It originates from the lumbar plexus in the lower back. From there, it extends downward, supplying the inner thigh. Its functions include controlling muscle movements and providing sensory feedback in this area.
Journey of the Obturator Nerve
The obturator nerve originates from the lumbar plexus, a network formed by the anterior divisions of the second, third, and fourth lumbar spinal nerves (L2, L3, L4). It descends through the psoas major muscle before emerging from its medial border.
The nerve then travels along the lateral wall of the pelvis, positioned behind the common iliac arteries. It exits the pelvic cavity by passing through the obturator canal, an opening within the obturator foramen. Upon entering the medial compartment of the thigh, the obturator nerve typically divides into an anterior and a posterior branch.
Muscles It Controls
The obturator nerve provides motor innervation to most of the muscles located in the medial compartment of the thigh. These muscles are primarily responsible for adduction, the action of bringing the thigh closer to the body’s midline. The anterior branch of the obturator nerve typically supplies the adductor longus, adductor brevis, and gracilis muscles.
The adductor longus muscle is a strong adductor of the thigh and also contributes to external rotation and some flexion of the thigh. The adductor brevis muscle also primarily adducts the thigh and assists with hip flexion. The gracilis muscle is a long, thin muscle that adducts the thigh, flexes the leg at the knee, and aids in internal rotation of the knee.
The posterior branch of the obturator nerve is responsible for innervating the adductor part of the adductor magnus and the obturator externus muscle. The adductor magnus is a powerful adductor of the thigh and its adductor portion also assists in thigh flexion. The obturator externus muscle functions mainly as an external rotator of the hip.
Sensory Areas It Serves
The obturator nerve also carries sensory information. It supplies sensation to a specific area of the skin located on the medial, or inner, aspect of the thigh. This sensory function is carried out by the cutaneous branches, particularly from its anterior division.
In addition to skin sensation, the obturator nerve provides articular branches, which supply sensory input to both the hip and knee joints. This allows the brain to receive information about the position and movement of these joints. Understanding these sensory contributions is important for diagnosing conditions affecting the obturator nerve, as altered sensation can be a key indicator of an issue.
When the Nerve is Affected
Damage or irritation to the obturator nerve can lead to a range of symptoms that impact both movement and sensation. Common causes of obturator nerve issues include trauma, compression from surrounding structures, complications arising from pelvic surgery, or childbirth. An obturator hernia, where tissue protrudes through the obturator foramen, can also compress the nerve. Sports injuries involving the hip and groin region are another frequent cause.
Individuals experiencing obturator nerve dysfunction often report weakness or difficulty with thigh adduction, making it challenging to bring their legs together. Pain is another common symptom, typically localized in the groin area or along the medial aspect of the thigh. Sensory changes may also occur, such as numbness, tingling, or an altered perception of pain, pressure, or temperature in the inner thigh region. These symptoms can significantly affect daily activities like walking, maintaining balance, and even simple leg movements.