Weakness of the quadriceps muscle and decreased patellar reflex are the most striking examination findings. If advanced and chronic, wasting of the quadriceps may also be present. In some patients, the iliopsoas muscle will be involved. In such cases, the lesion must be above the inguinal ligament, as the motor branch to this muscle comes off before the inguinal ligament. In isolated femoral neuropathies, the thigh adductors are normal.
Sensory deficits consist of numbness of the medial thigh and the anteromedial calf.
If a retroperitoneal hematoma is present, hip extension may cause pain. This is commonly associated with hemorrhage into this muscle due to hemophilia, anticoagulation therapy, or trauma. Direct trauma to the femoral nerve can occur as a result of penetrating wounds or fractures of the hip or pelvis. In this position, the sharp flexion of the hip can compress the nerve at the inguinal ligament. Excessive hip abduction and external rotation cause additional stretch on the nerve.