The Lumbosacral Nerve Plexus

The lumbar sacral nerve plexus can be divided into the direction the nerves travel, either anterior or posterior. This post will focus on anterior hip nerves. I remember writing about the brachial plexus over and over in physical therapy school, but only a few times for the lumbosacral plexus. Patients frequently report anterior hip and pubic pain and can often have signs and symptoms of nerve entrapment. This article orients the reader to links between signs and symptoms and examination to help appropriately diagnosis specific nerves in the athletic population.

The obturator, femoral and lateral femoral cutaneous are more commonly entrapped in sports injuries. Although the three nerves that travel together through the inguinal canal (ilioinguinal, iliohypogastric, and genitofemoral) are less common, however surgery can create nerve entrapment sequelae.

There are a few places where the obturator nerve can become squished. Typically, as it leaves the obturator canal which presents at medial thigh pain, and then again in the fascia of the adductors which presents as pain with abduction. The challenge is to differentiate between the nerve and adductor strain. Obturator nerve entrapment will test positive with passive hip abduction and extension, but negative resisted hip adduction.

The femoral nerve can become entrapped in a kind of compartment syndrome as it goes between the psoas and iliacus. This can lead to compression to the neurovascular bundle with resultant swelling, edema, and ischemia. Signs of femoral nerve compression include anterior thigh numbness and paresthesias. Occasionally, this can also include the saphenous nerve with symptoms continuing along medial knee to foot. Femoral nerve entrapment can create quadricep muscle weakness and atrophy, with diminished or absent patella tendon reflexes. Symptoms are reproduced with hip extension and knee flexion thereby elongating the femoral nerve.

The lateral femoral cutaneous (LFC) nerve is sensory. Diagnosed as meralgia paresthetica, the LFC nerve is typically entrapped where it penetrates under the inguinal ligament just medial to the anterior superior iliac spine (ASIS). Symptoms include numbness, tingling, hypersensitivity to touch, burning along outer thigh along the iliotibial band. The LFC nerve can often be compressed by wearing heavy belts (scuba divers, construction belts, etc). Special tests that indicate LFC are pelvic compression in side lying with involved side up to slack the inguinal ligament and Tinels sign.

Anterior hip pain is fairly common in pelvic floor patients. Differential diagnosis and treatment of these anterior nerves can allow patients to return to full daily function. To learn manual assessment and treatment techhniques for the lumbar nerves, consider attending Lumbar Nerve Manual Assessment and Treatment.

Martin R, Martin HD, Kivlan BR. Nerve Entrapment In The Hip Region: Current Concepts Review. Int J Sports Phys Ther. 2017 Dec;12(7):1163-1173.