Osteoarthritis

Osteoarthritis is the most common form of arthritis: a whole-joint disorder in which articular cartilage degrades while changes occur in the underlying bone, synovium, ligaments, and surrounding muscle. It typically presents with activity-related joint pain, stiffness, and progressive functional limitation, most often in the knees, hips, and hands.

Definition

Osteoarthritis is a chronic, degenerative joint disorder characterised by progressive loss of articular cartilage together with subchondral bone remodelling, osteophyte formation, and low-grade synovial inflammation, clinically expressed as joint pain and impaired function.

Scope

This entry describes osteoarthritis as a clinical entity within musculoskeletal medicine: its definition as a whole-joint disease, the main risk factors and pathological features, its epidemiologic burden, and the general evidence landscape. It is reference-educational and does not provide individualised treatment recommendations.

Key concepts

• Articular cartilage degradation
• Whole-joint disease concept
• Subchondral bone remodelling and osteophytes
• Activity-related joint pain and stiffness
• Mechanical loading and joint malalignment
• Obesity and metabolic risk factors
• Radiographic versus symptomatic disease

Mechanisms

Osteoarthritis is now understood as a disease of the whole joint rather than simple cartilage wear. Mechanical overload and biochemical changes drive degradation of the cartilage matrix, while the subchondral bone remodels and osteophytes form at joint margins; low-grade synovial inflammation and changes in periarticular ligaments and muscle contribute to pain and dysfunction. The relationship between structural damage seen on imaging and the symptoms a person experiences is imperfect, which is central to how the condition is assessed.

Clinical relevance

Osteoarthritis is a leading cause of chronic pain and disability, and its conservative management is a core concern of rehabilitation. Major guidelines converge on education, exercise, and weight management as foundational, non-pharmacological approaches. This description summarises the condition for reference and evidence appraisal and is not a substitute for individualised clinical assessment.

Epidemiology

Osteoarthritis affects hundreds of millions of people worldwide and is one of the fastest-growing contributors to years lived with disability, driven by population ageing and rising obesity; the Global Burden of Disease analyses document a substantial increase in prevalence over recent decades, with the knee and hip among the most affected joints.

History

Once regarded as inevitable 'wear and tear', osteoarthritis was reconceptualised over the late twentieth and early twenty-first centuries as an active, whole-joint disease process, a shift reflected in contemporary reviews and in guideline emphasis on modifiable risk factors and active management.

Debates

Why do structural changes and symptoms correlate poorly?

Radiographic severity often diverges from the pain and disability a person reports, complicating diagnosis and outcome measurement and motivating a whole-joint and biopsychosocial view of the disease.

Seminal works

• hunter-2019
• safiri-2020
• bannuru-2019

Frequently asked questions

Is osteoarthritis just 'wear and tear' of cartilage?

No. Although mechanical loading matters, osteoarthritis is considered a whole-joint disease involving cartilage, subchondral bone, synovium, ligaments, and muscle, with active biological processes rather than passive wear alone.

Which joints are most commonly affected?

The knees, hips, and hands are most frequently involved, though osteoarthritis can affect many joints, particularly with ageing and prior joint injury.