Facet joint hypertrophy (FJH) is a common spinal condition where the small joints located on the back of the vertebrae become enlarged and thickened. This condition is a frequent source of chronic back pain, affecting many people as they age. Hypertrophy refers to the abnormal increase in the size of the joint’s bone and soft tissues, often due to degenerative changes. While FJH may not always cause symptoms, the resulting joint enlargement can narrow the space for nerves, leading to pain and discomfort.
Understanding the Facet Joints and Hypertrophy
The spine is composed of stacked vertebrae, and the facet joints, also known as zygapophysial joints, connect one vertebra to the next. These paired, synovial joints are located on the posterior side of the spinal column. They are responsible for guiding movement while also limiting excessive motion like rotation and hyperextension. Like other joints in the body, the surfaces of facet joints are covered with cartilage, surrounded by a joint capsule, and lubricated by synovial fluid.
The primary function of these joints is to stabilize the spine, bearing up to 20% of the compressive forces that act vertically on the back. Hypertrophy occurs when this joint structure abnormally enlarges, which typically involves the overgrowth of bone, known as osteophytes or bone spurs, and the thickening of the surrounding joint capsule and soft tissues. This process is the body’s attempt to stabilize a segment of the spine that has become unstable due to wear and tear.
Root Causes and Contributing Factors
Facet joint hypertrophy is overwhelmingly a consequence of age-related degeneration, a process often referred to as osteoarthritis or spondylosis. Over many years, the cartilage cushioning the joint surfaces begins to wear down, reducing its ability to absorb shock and leading to friction between the bones. This bone-on-bone contact triggers a defensive biological response where the body attempts to repair the damage by creating new bone tissue.
The formation of bone spurs and the thickening of the joint capsule are manifestations of this attempt at stabilization, which ultimately results in the joint’s enlargement. A major biomechanical factor contributing to this is the degeneration of the intervertebral discs that sit between the vertebral bodies. As these discs lose height and integrity, the increased load is transferred to the posterior facet joints, accelerating the degenerative changes and the hypertrophic process. Repetitive mechanical stress, previous trauma, poor posture, and excessive body weight can also contribute to this cycle of wear and compensatory overgrowth.
Recognizing the Pain and Symptoms
The main symptom associated with FJH is localized back pain and stiffness, most commonly felt in the lumbar or lower back region. This discomfort is often described as a dull ache or throbbing pain that is centered near the spine. A characteristic feature of facet joint pain is that it tends to worsen when the spine is put into extension, such as when leaning backward, standing for long periods, or getting out of a chair.
Conversely, individuals often experience some relief when they flex the spine, such as by sitting, leaning forward, or walking with a forward stoop. When the joint enlargement becomes significant, it can narrow the space available for the spinal nerves, a condition known as spinal stenosis. This narrowing can irritate or compress the nerves, causing radicular pain, which is sharp, shooting pain, numbness, or tingling that travels down the arms or legs. Stiffness, particularly in the morning or after periods of inactivity, is also a frequent complaint.
Diagnosis and Management Strategies
The process of diagnosing facet joint hypertrophy begins with a detailed physical examination and a review of the patient’s symptoms, focusing on movements that provoke or relieve the pain. Imaging tests are then used to visualize the spinal structures and confirm the presence and extent of the joint enlargement. X-rays can reveal bony overgrowth and alignment issues, while a computed tomography (CT) scan provides superior detail on the bone spurs and the degree of neural narrowing.
Magnetic resonance imaging (MRI) is often considered the most informative tool, as it shows the joint enlargement, soft tissue inflammation, and any resulting nerve compression. The definitive diagnostic step involves a diagnostic facet joint injection, also known as a medial branch block. This procedure involves injecting a small amount of numbing medication near the medial branch nerves that transmit pain signals from the joint. If the patient experiences significant, temporary pain relief, it confirms the facet joint as the source of the discomfort.
Management of facet joint hypertrophy typically begins with conservative approaches aimed at reducing inflammation and improving function. Physical therapy is a major component, focusing on core muscle strengthening and improving posture to stabilize the spine and reduce stress on the joints. Over-the-counter non-steroidal anti-inflammatory drugs (NSAIDs) can help manage pain and inflammation.
If conservative methods prove insufficient, more advanced treatments may be considered. Therapeutic facet joint injections deliver a mixture of a local anesthetic and a corticosteroid directly into the joint space for longer-lasting relief from inflammation. For patients who receive temporary but reliable relief from these injections, radiofrequency ablation (RFA) is a common next step. RFA uses heat to temporarily interrupt the function of the specific medial branch nerves, with relief often lasting between six and twelve months. Surgery is typically reserved for severe cases, such as when significant nerve compression causes progressive neurological symptoms or when all other treatments have failed, and may involve decompression or spinal fusion.