The femoral nerve is located in the leg and supplies the muscles that help straighten the leg. It supplies sensation to the front of the thigh and part of the lower leg.

Dysfunction of a single nerve group such as the femoral nerve is classed as mononeuropathy. Mononeuropathy implies a local cause of the nerve damage, although systemic disorders may occasionally cause isolated nerve damage (such as occurs with mononeuritis multiplex).

The usual causes are direct trauma, prolonged pressure on the nerve, and compression of the nerve by nearby body structures or pathologic structures (such as a tumor). Prolonged pressure may be complicated by ischemia (lack of oxygen from decreased blood flow) in the area.

Entrapment involves pressure on the nerve where it passes through a narrow structure. The damage includes destruction of the myelin sheath of the nerve or destruction of part of the nerve cell (the axon). This damage slows or prevents passage of impulses through the nerve.

The femoral nerve can be injured as a result of pelvic fractures. It may be injured during catheterization of the femoral artery. It can be affected by systemic diseases causing polyneuropathy (damage to multiple nerves) such as diabetes mellitus or polyarteritis nodosa. It can be damaged by pressure from lesions such as tumor, abscess, or internal bleeding into the pelvis or abdomen.

One common risk factor is lying in the "lithotomy" position (on the back with thighs and legs flexed) during surgery or diagnostic procedures. In some cases, no detectable cause can be identified.