osteoarthritis

osteoarthritis. It is the most common form of arthritis, characterized by the breakdown of articular cartilage and underlying bone within a synovial joint. This progressive disorder leads to pain, stiffness, and functional impairment, significantly impacting quality of life. While it can affect any joint, it most commonly involves the knee, hip, hand, and spine.

Signs and symptoms

The cardinal symptom is deep, aching joint pain that typically worsens with activity and is relieved by rest. Morning stiffness is common but usually lasts less than thirty minutes, unlike in rheumatoid arthritis. Patients often experience crepitus, a grating sensation or sound during joint movement, and may notice visible bony enlargement at affected sites like the distal interphalangeal joints, known as Heberden's nodes. Reduced range of motion and joint instability can lead to functional limitations, such as difficulty with climbing stairs or grip strength. In advanced stages, joint effusion and mild synovitis may occur, and deformities like genu varum can develop in the knee.

Causes and risk factors

The etiology is multifactorial, involving a complex interplay of systemic factors and local biomechanics. Advancing age is the strongest associated risk factor, with prevalence increasing dramatically after age 50. Genetic predisposition plays a significant role, with genes like GDF5 and COL2A1 implicated, particularly in hand osteoarthritis. Female sex confers a higher risk, especially after menopause, suggesting a role for estrogen. Obesity is a major modifiable risk factor due to increased mechanical load and systemic inflammation. Prior joint injury, such as an anterior cruciate ligament tear or meniscal tear, is a common cause of secondary disease. Repetitive stress from certain occupational hazards, like farming or jobs requiring heavy lifting, and participation in elite sports like football are also contributory.

Pathophysiology

The disease process involves the entire synovial joint as an organ. Initial changes occur in the articular cartilage, where an imbalance between anabolic and catabolic activity leads to matrix degradation. Chondrocytes produce inflammatory cytokines such as interleukin-1 and tumor necrosis factor, which stimulate enzymes like matrix metalloproteinases that break down collagen and proteoglycans. Concurrently, the underlying subchondral bone undergoes sclerosis and remodeling, with formation of osteophytes at the joint margins. The synovium often exhibits low-grade inflammation, and the joint capsule can thicken. These changes alter joint biomechanics, creating a cycle of progressive damage and pain pathway activation through nociceptors in periarticular tissues.

Diagnosis

Diagnosis is primarily clinical, based on history and physical examination findings of pain, bony enlargement, and limited movement. Radiography is the main imaging modality used for confirmation, with classic features including joint space narrowing, osteophyte formation, subchondral sclerosis, and subchondral cysts. The Kellgren–Lawrence grading system is commonly used to classify severity on radiographs. Magnetic resonance imaging is more sensitive for detecting early cartilage lesions, bone marrow lesions, and meniscal pathology, but is not routinely required. Blood tests are typically normal but are used to exclude other arthritides like rheumatoid arthritis (e.g., rheumatoid factor, anti-CCP) or gout (serum uric acid). Synovial fluid analysis usually shows a non-inflammatory fluid with a white cell count below 2000/µL.

Management

Management is tailored to symptom severity and focuses on pain relief and functional improvement. Core non-pharmacological treatments include patient education, weight loss programs, and structured exercise therapy, particularly aerobic exercise and muscle strengthening. Physical therapy can provide gait training and prescribe assistive devices like a cane or knee brace. First-line pharmacological therapy is paracetamol or topical NSAIDs like diclofenac. Oral NSAIDs (e.g., naproxen, celecoxib) are used with caution due to risks of gastrointestinal bleeding and cardiovascular disease. For knee or hip involvement, intra-articular injection of corticosteroids provides short-term relief, while hyaluronic acid injections are an option in some regions. For severe, refractory pain and disability, surgical interventions such as arthroscopy, osteotomy, or joint replacement (e.g., total knee arthroplasty, total hip arthroplasty) are definitive treatments.

Epidemiology

It is a leading cause of chronic disability worldwide and a major contributor to global burden of disease. Prevalence increases with age, affecting over 10% of men and 18% of women over 60 globally. The knee is the most commonly affected joint. Incidence is rising due to aging populations and the obesity epidemic. Significant geographic and ethnic variations exist; for instance, prevalence of hip disease is lower in East Asia compared to Caucasian populations in Europe and North America. It results in substantial healthcare costs and economic burden from work disability and joint replacement surgeries, placing major demands on health systems like the National Health Service and Medicare. Category:Rheumatology Category:Orthopedic surgery Category:Geriatrics