Femoral Nerve Palsy: Causes, Symptoms, and Acupuncture Treatment

Femoral nerve palsy is a clinical syndrome caused by various factors, resulting in muscle paralysis and functional decline within the distribution of the femoral nerve.

The femoral nerve originates from L2–L4, runs obliquely downward and laterally between the psoas major and iliacus muscles, then crosses anteriorly over the psoas major near the inguinal ligament, lying medial to the psoas major and lateral to the femoral artery. It gives off muscular branches, cutaneous branches, and the saphenous nerve. – **Muscular branches** innervate the iliacus and psoas major, which flex and laterally rotate the thigh; when the leg is fixed, they flex the lumbar spine and tilt the trunk forward. – **Sartorius muscle**: flexes the hip and knee joints and laterally rotates the thigh; when the leg is fixed, it also flexes the lumbar spine and tilts the trunk forward. – **Pectineus muscle**: flexes, adducts, and laterally rotates the thigh. – **Quadriceps femoris muscle**: flexes the thigh and extends the leg.

Cutaneous branches: Distributed to the skin of the medial thigh down to the medial knee (medial branch) and to the skin of the anterior thigh extending to the ilium (lateral branch).

Saphenous nerve: This is a long nerve arising from the femoral nerve at or slightly above the level of the inguinal ligament. In the femoral sheath, it lies lateral to the femoral artery; in the mid-thigh, it lies anterior to the femoral artery and enters the adductor canal together with the artery. It pierces the anterior wall of the canal, descends along the lower border of the sartorius muscle, and reaches the medial side of the knee. At the medial knee, it gives off a cutaneous branch (the infrapatellar branch) to the skin over the medial knee and patella, as well as to the medial, anterior, and posterior aspects of the lower leg, the medial border of the foot, and the skin over the base of the toes (i.e., the skin of the medial side of the lower leg).

There are many causes of femoral nerve palsy, common ones include:

1. Tumors: Pelvic tumors, spinal cord tumors, vertebral tumors, retroperitoneal tumors, etc.

2. Surgery and trauma: Inguinal region surgery, pelvic trauma, etc.

3. Abscess or hematoma: psoas major abscess or hematoma.

4. Other: Aneurysm of the lower limbs, Diabetes (Xiaoke), lead poisoning, organophosphate pesticide poisoning, and improper posture such as excessive extension or external rotation of the thigh during coma or anesthesia can all cause femoral nerve injury.

Diagnostic Key Points

The main clinical manifestations include difficulty flexing the knee joint, inability to extend the knee, and atrophy of the anterior thigh muscles. The patient walks with a short-stepped gait, first stepping forward with the unaffected limb and then dragging the affected limb forward. Running and jumping are impossible, and climbing stairs is limited. Sensation on the anterior aspect of the thigh, the medial aspect of the lower leg, and the medial side of the foot is decreased or absent. Occasionally, there may be significant pain in the knee.

Treatment

1. Acupoints and Acupuncture Techniques

1. ST31 (Biguan), affected side: Located on the line connecting the anterior superior iliac spine and the lateral border of the patella, at the level of the gluteal fold. A 30-gauge, 2-cun filiform needle is inserted approximately 1.8 cun toward the medial aspect of the femur after routine local disinfection. Needle sensation: local distension and pain, or radiation toward the knee joint.

2. **SP11 (Jimen)** (affected side): Located 6 *cun* above SP10 (Xuehai), on the medial border of the sartorius muscle. After routine local disinfection, insert a 30-gauge, 2 *cun* filiform needle vertically toward the femur to a depth of approximately 1.8 *cun*. Needling sensation: Local distension and pain, or a radiating sensation toward the medial aspect of the lower leg.

3. **SP10 (Xuehai) on the affected side**: With the knee flexed, locate the point 2 cun directly above the medial superior border of the patella, at the bulge of the medial head of the quadriceps femoris muscle. Use a 30-gauge, 2-cun filiform needle. After routine local disinfection, insert perpendicularly to a depth of approximately 1.8 cun. Needling sensation: local distension and pain.

4. ST32 (Futu) on the affected side: Located on the line connecting the anterior superior iliac spine and the lateral border of the patella, 6 cun above the superior border of the patella. Use a 30-gauge, 2-cun filiform needle. After routine local disinfection, insert perpendicularly toward the medial border of the femur to a depth of about 1.8 cun. Needling sensation: Local distension and pain.

5. SP9 (Yinlingquan) on the affected side: Located in the depression inferior to the medial condyle of the tibia. Use a 30-gauge, 2 cun filiform needle. After routine local disinfection, insert perpendicularly toward the fibula to a depth of approximately 1.6 cun. Sensation: Local distension and pain.

6. **Heding (EX-LE2)** (affected side): Located in the upper knee region, in the depression at the midpoint of the superior border of the patella. Using a 30-gauge, 2.5 cun filiform needle, after routine local disinfection, insert obliquely towards ST32 (Futu) to a depth of approximately 2.3 cun. Needling sensation: local distension and pain, or a radiating sensation toward the inguinal region.

7. SP6 (Sanyinjiao) on the affected side: Located 3 cun above the medial malleolus on the posterior border of the medial surface of the tibia. After routine local disinfection, insert a gauge-30, 1.5-cun filiform needle perpendicularly toward GB39 (Xuanzhong) to a depth of approximately 1.3 cun. The needling sensation is local distension and pain.

2. Methods

The patient assumes a supine position. The above points are needled according to the standard technique, with electroacupuncture applied. Needles are retained for 40 minutes. After needle removal, cupping is performed for about 1 minute. Treatment is administered once daily, with 10 sessions constituting one course of treatment. A 5-day rest is taken before the next course.

[Commentary]

This condition has many secondary disorders, so electroacupuncture should be applied alongside treatment of the secondary disorders. Generally, patients in the early stage without obvious muscle atrophy respond better to treatment. For those with muscle atrophy, a longer course of treatment is required; however, with patience, satisfactory results can still be achieved. The degree of recovery is primarily related to the resolution of the underlying cause of the secondary disorders.

Etiology and Pathophysiology of Femoral Nerve Palsy

The causes of femoral nerve palsy are diverse, reflecting the nerve’s anatomical vulnerability as it courses from the lumbar plexus (L2–L4) through the retroperitoneal space and beneath the inguinal ligament. Iatrogenic injury during pelvic or orthopedic procedures—such as total hip arthroplasty, inguinal hernia repair, or renal transplantation—represents a significant predisposing factor. Direct trauma, including pelvic fractures and penetrating wounds, can also disrupt axonal integrity. In non‐traumatic settings, compressive lesions from retroperitoneal hematomas (frequently associated with anticoagulation therapy), psoas abscesses, or neoplasms (e.g., lymphoma or colorectal carcinoma) are well‐documented. Additionally, ischemic insult due to prolonged lithotomy positioning or intraoperative stretch may compromise microvascular perfusion. Metabolic and inflammatory conditions, such as diabetes mellitus, vasculitis, and radiation‐induced fibrosis, further contribute to neuropathy. Understanding these multifactorial origins is essential for targeted prevention and early intervention. The nerve’s intimate relationship with the iliacus and psoas muscles renders it susceptible to both extrinsic compression and intrinsic traction forces, underscoring the need for careful clinical assessment of any patient presenting with unilateral lower‐limb weakness or sensory loss.

Clinical Manifestations and Diagnostic Challenges

The femoral nerve paralysis symptoms reflect the nerve’s motor and sensory territories, leading to a characteristic yet often underrecognized clinical picture. Patients typically report difficulty in hip flexion and knee extension, resulting in an unstable gait and inability to ascend stairs. On examination, weakness of the iliopsoas and quadriceps femoris muscles is evident, often accompanied by atrophy of the vastus medialis in chronic cases. Sensory deficits involve the anterior and medial thigh, extending down the medial leg to the medial malleolus via the saphenous nerve. Pain, though variable, may manifest as dysesthesia or burning in the same distribution. Crucially, the patellar reflex is diminished or absent. Differentiating femoral neuropathy from lumbar radiculopathy or plexopathy requires careful electrophysiological studies, including nerve conduction velocity and needle electromyography. Imaging—particularly high‐resolution ultrasound or magnetic resonance neurography—can identify structural lesions such as hematomas or space‐occupying masses. Clinicians must remain vigilant for associated conditions, as delayed diagnosis may prolong disability and compromise functional recovery. Accurate recognition of these symptoms is the cornerstone of appropriate management, guiding the selection of further investigative and therapeutic measures.

Therapeutic Strategies and Prognosis

Optimal femoral nerve palsy treatment options are guided by etiology, severity, and chronicity, emphasizing a multidisciplinary approach. For acute compressive lesions (e.g., retroperitoneal hematoma), urgent surgical decompression or percutaneous drainage can restore nerve function if performed within hours to days. Iatrogenic transections or neuroma formation may require microsurgical neurorrhaphy or nerve grafting, though outcomes are variable. Non‐operative management forms the mainstay for mild to moderate cases: physical therapy focused on quadriceps strengthening, gait retraining, and range‐of‐motion exercises reduces contracture risk. Pharmacologically, neuropathic pain agents (e.g., gabapentin, pregabalin) and nonsteroidal anti‐inflammatory drugs provide symptomatic relief. In patients with underlying metabolic or inflammatory disease, optimization of glycemic control or immunosuppressive therapy is paramount. Emerging adjuncts such as transcutaneous electrical nerve stimulation or regenerative therapies (e.g., platelet‐rich plasma injections) remain under investigation. Prognosis correlates with the degree of axonal sparing: incomplete lesions often yield substantial recovery over months, whereas complete denervation may lead to persistent weakness. Early recognition and tailored intervention—whether conservative or surgical—are critical to maximizing functional outcome and minimizing long‐term disability.