The obturator nerve is one of the largest branches of the lumbar plexus. It is a mixed nerve which arises from the ventral (anterior) rami of the spinal nerves L2-L4.
The function of the obturator nerve is to provide motor innervation to all the medial muscles of the thigh (hip adductors) except for the hamstring part of the adductor magnus. In addition, the nerve provides sensory innervation to the skin over the proximal part of the medial thigh and articular branch for the hip and knee joints.
This article will describe the anatomy and function of the obturator nerve.
|Origin||Lumbar plexus (L2-L4)|
Motor: Adductor longus, adductor brevis, gracilis, obturator externus and ischiocondylar part of adductor magnus muscle.
Sensory: Skin of the proximal part of the medial thigh, hip joint and knee joint.
Origin and course
The anterior roots of spinal nerves L2, L3 and L4 unite near the iliac crest, forming the obturator nerve. The nerve descends through the fibers of the psoas major muscle and emerges from its medial border near the pelvic brim to enter the lesser pelvis.
Here, the nerve runs on the lateral wall of the pelvis, posterior to the common iliac artery and lateral to the internal iliac vessels. Then, it exits the pelvis by passing through the obturator canal and to enter the medial compartment of the thigh.
Learn more about all the branches of the lumbar plexus here:
Branches and function
The obturator nerve has two branches and they both arise in the thigh, just after the nerve traverses the obturator canal:
- The anterior branch (or division) of the obturator nerve passes deep to the adductor longus and over the surface of the adductor brevis muscle. In cadavers, you would find it sandwiched between these two muscles. This nerve ramifies into cutaneous and muscular branches. The former innervate the overlying skin of the medial thigh and the hip joint, while the latter supply the adductor longus, adductor brevis and gracilis muscles.
- The posterior branch (division) of the obturator nerve pierces the obturator externus and then passes over the adductor magnus. It supplies both of these muscles and gives articular branches that supply the capsule of the knee joint. Note that the obturator nerve supplies only the ischiocondylar part of the adductor magnus, while its adductor part is supplied by the tibial nerve.
To sum up, the obturator provides motor innervation to the adductor longus, adductor brevis, gracilis, obturator externus and ischiocondylar part of adductor magnus muscle. Its cutaneous distribution covers the skin of the proximal part of the medial thigh, as well as the hip and knee joints.
Want to test your knowledge on the innervation patterns of the lower limb muscles? Try this fully customizable quiz:
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