Osteoarthritis

Osteoarthritis (OA) is the most common chronic joint disorder and the leading cause of disability among adults worldwide. It is a degenerative synovial joint disease characterized by progressive loss of articular cartilage, remodeling of subchondral bone, osteophyte formation, synovial inflammation, capsular thickening, and peri-articular muscle weakness.

Historically considered a purely “wear-and-tear” disease, modern understanding shows OA is a whole-joint disease involving biochemical, inflammatory, mechanical, metabolic, and genetic mechanisms.

Pathological hallmarks

• Progressive articular cartilage degeneration

• Subchondral bone sclerosis and cyst formation

• Osteophyte formation (bony spurs)

• Synovitis (low-grade inflammation)

• Ligament laxity and meniscal degeneration

• Joint space narrowing

Commonly affected joints

• Knee (most common)

• Hip

• Cervical and lumbar spine

• Distal interphalangeal joints (Heberden’s nodes)

• Proximal interphalangeal joints (Bouchard’s nodes)

• First carpometacarpal joint (base of thumb)

Etiology

Cause is multifactorial rather than a single factor.

Risk factors

• Increasing age

• Female sex

• Obesity

• Previous joint injury

• Occupational overuse

• Sports stress

• Genetic predisposition

• Muscle weakness

• Joint malalignment

• Metabolic disorders (e.g., diabetes, metabolic syndrome)

Pathophysiology (Stepwise)

1. Chondrocyte injury → cytokine release (IL-1, TNF-α)

2. Matrix metalloproteinases degrade collagen & proteoglycans

3. Cartilage softening → fibrillation → erosion

4. Bone exposure → sclerosis

5. Osteophyte formation

6. Chronic pain and loss of function

Signs and Symptoms

Pain characteristics

• Deep aching joint pain

• Worse with activity

• Relieved by rest

• Morning stiffness < 30 minutes

• Pain at end of day

Functional symptoms

• Reduced mobility

• Joint instability

• Difficulty climbing stairs

• Reduced grip strength (hand OA)

• Limping (hip/knee OA)

Mechanical symptoms

• Crepitus

• Locking (due to loose bodies)

• Joint giving way

Physical examination findings

• Bony enlargement

• Tenderness along joint line

• Reduced range of motion

• Effusion (especially knee)

• Deformity (varus/valgus knee)

Classic deformities

• Heberden’s nodes (DIP joints)

• Bouchard’s nodes (PIP joints)

• Squaring of thumb base

• Genu varum (bow-leg knee)

Diagnostic Criteria

Diagnosis is mainly clinical supported by imaging.

Clinical features

• Activity-related joint pain

• Age > 45 years

• Morning stiffness < 30 min

• Crepitus

• Bony enlargement

• Absence of systemic inflammation

Classification (American College of Rheumatology)

Knee OA likely if:

• Knee pain PLUS ≥3 of:

  • Age >50

  • Morning stiffness <30 min

  • Crepitus

  • Bony tenderness

  • Bony enlargement

  • No warmth

Investigations

Imaging

Plain X-ray (gold standard)Typical findings:

• Joint space narrowing (asymmetric)

• Osteophytes

• Subchondral sclerosis

• Subchondral cysts

Advanced imaging

• MRI: early cartilage damage

• CT: complex joints

• Ultrasound: effusion/synovitis

Laboratory tests (usually normal)

Used to exclude inflammatory arthritis

• ESR: normal

• CRP: normal

• Rheumatoid factor: negative

• Anti-CCP: negative

• Synovial fluid: non-inflammatory (<2000 WBC/mm³)

Management

Goals:

• Reduce pain

• Improve function

• Slow progression

• Improve quality of life

Non-Pharmacological Treatment (First-Line)

Patient education

• Chronic but manageable condition

• Avoid joint overloading

• Encourage activity, not rest

Exercise therapy (most effective intervention)

• Quadriceps strengthening

• Range-of-motion exercises

• Aerobic exercises (walking, cycling, swimming)

Weight reduction

• Every 1 kg lost → 4 kg less knee load

Assistive devices

• Cane (opposite side hand)

• Knee brace

• Shoe insoles

• Walkers

Physiotherapy

• Muscle strengthening

• Posture correction

• Heat therapy

• Hydrotherapy

Occupational modifications

• Avoid squatting

• Avoid kneeling

• Avoid heavy lifting

Pharmacological Treatment

Stepwise approach

1. First-line analgesic

Paracetamol

• 500–1000 mg PO 6–8 hourly

• Max 4 g/day

2. NSAIDs (if pain persists)

Ibuprofen

• 200–400 mg PO 8 hourly

OR

Diclofenac

• 50 mg PO 8 hourly

OR

Naproxen

• 250–500 mg PO 12 hourly

Always assess GI and renal riskConsider PPI in elderly

3. Topical therapy (preferred in elderly)

• Topical diclofenac gel

• Capsaicin cream

4. Moderate to severe pain

Tramadol

• 50–100 mg PO 8–12 hourly

5. Intra-articular therapy

• Corticosteroid injection (short-term relief)

• Hyaluronic acid (viscosupplementation)

6. Supplements (variable benefit)

• Glucosamine sulfate

• Chondroitin sulfate

Surgical Treatment

Indications:

• Severe pain

• Functional disability

• Failure of conservative treatment

• Advanced radiological disease

Procedures

• Arthroscopic debridement (limited role)

• Osteotomy (young patients)

• Total joint replacement

  • Total knee replacement

  • Total hip replacement

Complications

• Chronic disability

• Joint deformity

• Muscle wasting

• Falls

• Depression

• Reduced quality of life

Prevention

Primary prevention

• Maintain normal weight

• Avoid joint injuries

• Proper sports technique

• Ergonomic workplace

Secondary prevention

• Early physiotherapy

• Strengthening exercises

• Correct malalignment

• Treat metabolic syndrome

Tertiary prevention

• Assistive devices

• Joint protection strategies

• Rehabilitation

Prognosis

• Slowly progressive disease

• Many patients remain functional

• Severe cases may require joint replacement

• Not life-threatening but disabling