Osteoarthritis is a joint condition characterized by the breakdown of cartilage, the protective tissue at the ends of bones, leading to pain and stiffness. While this discomfort is often linked to the joint itself, a different type of pain, known as neuropathic pain, can also develop. This pain originates from the nerves, not the joint, creating a more complex pain profile for those with osteoarthritis.
The Source of Nerve Pain in Osteoarthritis
A direct cause of nerve-related pain in osteoarthritis is mechanical compression. As cartilage wears away, the body may grow extra bone, called osteophytes or bone spurs, along the joint’s edges. These growths can press on or “pinch” nearby nerves. This is common in the spine, where bone spurs can narrow nerve pathways, leading to radiating pain.
Chronic inflammation within the arthritic joint is another source of nerve pain. The inflammatory process releases biochemicals, like cytokines and prostaglandins, into the joint space. These substances can irritate and sensitize the endings of nearby peripheral nerves. Over time, this chemical exposure can damage the nerves, causing them to send abnormal pain signals to the brain.
Persistent pain signals from an arthritic joint can lead to central sensitization. This condition involves a “rewiring” of the central nervous system, making the spinal cord and brain hyperexcitable. Constant pain input makes neurons more responsive, amplifying the signals they send to the brain. As a result, the nervous system may interpret light touch or normal movement as painful, causing pain that seems disproportionate to the joint damage.
Identifying Neuropathic Symptoms
Neuropathic pain feels distinctly different from standard osteoarthritis pain. The typical joint pain, called nociceptive pain, is often a dull, deep ache localized to the joint that worsens with movement. This pain is a direct response to tissue damage.
In contrast, neuropathic pain indicates that the nerves themselves are malfunctioning. Patients often report a constant burning or searing sensation. Other common descriptions include sharp, shooting, or electric shock-like pains that can appear suddenly without a clear trigger.
Tingling, numbness, and radiating pain are also hallmarks of nerve involvement. Radiating pain is discomfort that travels along a specific nerve path. For example, nerve pain from an arthritic hip or lower spine can travel down the length of the leg.
The Diagnostic Process
Diagnosing neuropathic pain in osteoarthritis begins with a detailed discussion of symptoms. A physician will ask the patient to describe their pain, and using words like “burning,” “tingling,” or “shooting” suggests nerve involvement. Clinicians may also use specialized questionnaires to help identify neuropathic symptoms.
A physical examination looks for objective signs of nerve dysfunction. The doctor will test reflexes, muscle strength, and sensation near the affected joint. Diminished reflexes or muscle weakness can suggest a nerve is compressed or not functioning correctly, helping to pinpoint the issue’s location.
Imaging studies can identify structural causes of nerve pain. While an X-ray shows bone spurs and joint degeneration, it cannot visualize nerves. A magnetic resonance imaging (MRI) scan may be ordered to see soft tissues. An MRI can reveal if a nerve is being compressed by a bone spur, herniated disc, or inflamed tissue.
Management and Treatment Approaches
Treating the nerve pain of osteoarthritis requires a different strategy from managing standard joint pain. Medications targeting the nervous system are often more effective than traditional anti-inflammatories. Anticonvulsants like gabapentin and pregabalin can calm overactive nerve signals. Certain antidepressants, such as duloxetine, also help modulate pain signals in the central nervous system.
Topical treatments applied directly to the skin can provide localized relief, especially for joints like the hands and knees. Lidocaine patches deliver a numbing agent that blocks local nerve signals. Capsaicin cream, derived from chili peppers, works by desensitizing nerve endings over time to reduce their ability to transmit pain.
Physical and occupational therapy are important for managing nerve pain. A physical therapist can design exercises to relieve pressure on nerves, improve flexibility, and strengthen supporting muscles. An occupational therapist can teach new ways to perform daily activities that avoid aggravating the pain.
For persistent pain, interventional procedures may be an option. A nerve block involves injecting an anesthetic and a corticosteroid around the affected nerve to interrupt pain signals and reduce inflammation. Another procedure, radiofrequency denervation, uses an electrical current to heat and destroy specific nerve fibers, which can provide relief for a year or more.
Surgery may be an option for severe nerve compression that does not respond to other treatments. Decompression surgery aims to physically remove the source of pressure on the nerve, such as a bone spur or herniated disc. This approach is reserved for individuals with significant functional impairment or progressive neurological symptoms.