Peripheral neuropathy is a condition most commonly associated with symptoms in the hands and feet. This nerve damage can also significantly affect the knee area, leading to pain and dysfunction often mistaken for standard joint issues like arthritis or tendonitis. The knee contains an intricate network of nerves susceptible to injury and systemic disease. Recognizing that a problem at the knee may stem from a neurological source is the first step toward finding the correct diagnosis and treatment.
The Neurological Connection to the Knee
The knee joint receives sensory and motor information from several major nerves descending from the hip and pelvis. The sciatic nerve, the largest nerve in the body, splits just above the knee into the tibial nerve and the common peroneal (fibular) nerve. Both supply the lower leg and foot, with branches contributing to the knee joint itself. The common peroneal nerve wraps around the outside of the leg, making it vulnerable to compression near the fibular head.
The femoral nerve, originating in the lumbar spine, contributes the saphenous nerve and other branches that provide sensation to the front and inner side of the knee. A specialized network of sensory fibers called genicular nerves supplies the joint capsule and relays pain signals directly from the joint. Because these nerves originate higher in the body, damage in the spine, such as lumbar radiculopathy, can project pain down into the knee region, a phenomenon known as referred pain.
Recognizing Neuropathic Knee Symptoms
Neuropathic symptoms around the knee differ from the mechanical ache typically associated with joint wear and tear. Sensory manifestations often include abnormal sensations, such as pins and needles (paresthesia) or persistent numbness. Patients frequently describe a burning, sharp, or electric-shock-like pain, distinct from a dull joint ache.
Extreme sensitivity to touch, known as allodynia, may occur where even light pressure causes discomfort. This nerve-related pain is often constant and can worsen at night, disrupting sleep patterns. Mechanical joint pain, conversely, is typically aggravated by movement or weight-bearing activities and relieved by rest.
Motor symptoms also point toward a neuropathic cause, especially if the common peroneal nerve is involved. Damage to this nerve can lead to weakness in the muscles that lift the foot, potentially causing foot drop. This weakness manifests as difficulty clearing the toes while walking, leading to a steppage gait or instability around the knee joint.
Common Causes of Lower Limb Neuropathy Affecting the Knee
Neuropathy affecting the knee stems from systemic diseases that damage nerves throughout the body or from localized trauma or compression. Diabetes is the most frequent systemic cause of peripheral neuropathy, as high blood sugar levels progressively damage nerve fibers, often starting in the lower extremities. Other systemic issues include nutritional deficiencies, such as a lack of B vitamins, or side effects from certain chemotherapy drugs.
Localized causes involve direct mechanical pressure or injury to the nerve pathways. Sciatica, resulting from a herniated disc or spinal stenosis, can compress nerve roots, leading to pain that radiates to the knee. Trauma, such as a fracture or knee dislocation, can stretch or compress the common peroneal or tibial nerves near the joint.
Iatrogenic injury, or damage caused by a medical procedure, can occur following knee surgeries like total knee replacement. Nerves are susceptible to stretching or accidental injury during these procedures, or they may be compressed by post-operative swelling. External compression from prolonged positioning, such as squatting, can also lead to temporary or chronic neuropathy near the fibular head.
Diagnosis and Treatment Approaches
Diagnosing neuropathy around the knee requires a comprehensive approach to distinguish it from joint or soft tissue problems. A physician will conduct a thorough physical examination, testing reflexes, strength, and sensation patterns. Specialized tests, such as nerve conduction studies (NCS) and electromyography (EMG), are often performed to measure how well electrical signals are transmitted through the nerves and muscles.
Imaging tests, including magnetic resonance imaging (MRI) or high-resolution ultrasound, may be used to visualize the nerves and surrounding structures. These tools help identify structural causes, such as nerve compression from a herniated disc, tumor, or localized entrapment. Correct identification of the underlying cause guides the subsequent treatment plan.
Treatment aims to manage symptoms and address the root cause of the nerve damage. For systemic conditions like diabetes, strict blood sugar control is important to prevent further nerve deterioration. Symptom management often involves specific medications that work on nerve pain, such as certain anticonvulsants or antidepressants. Physical therapy plays a significant role in maintaining muscle strength and mobility, especially where motor weakness is present. If a nerve is severely compressed and not responding to conservative measures, surgical intervention may be necessary to relieve the pressure.