Osteoarthritis

Related Subjects: |Monoarticular arthritis |Polyarticular arthritis |Rheumatoid arthritis |Gout |Pseudogout |Septic Arthritis |Systemic Lupus Erythematosus (SLE) |Enteropathic Spondyloarthritis |Reactive Arthritis |Hip Osteoarthritis |Oxford Hip Score

Osteoarthritis (OA) is the most common joint disease. 🕑 Morning stiffness <30 min is a classic feature (vs. RA stiffness >1 hr). Think: “Cartilage loss → bone changes → pain and stiffness.”

📖 About

• OA = progressive degeneration of articular cartilage + secondary bone changes.
• Strongly age-related – affects ~70% of people >70 yrs.
• More common in ♀, white ethnicity, and those with family history.
• Polygenic heritability; not “just wear and tear.”

🦴 Main Joints Affected

• Hands 🤲 (DIP = Heberden’s nodes; PIP = Bouchard’s nodes)
• Knees 🦵 (varus/valgus deformity, Baker’s cyst)
• Hips 🦴 (pain may radiate to knee)
• Spine 🧍 (cervical, lumbar apophyseal joints)

⚙️ Aetiology / Pathophysiology

• Loss of hyaline cartilage + failure of repair → bone remodelling.
• Subchondral sclerosis, cysts, osteophyte formation (bony spurs).
• Mediators: metalloproteinases, IL-1, TNF impairing collagen repair.

🔄 Secondary OA

• Post-trauma, metabolic (haemochromatosis, ochronosis), endocrine (acromegaly).
• Chondrocalcinosis, congenital hip dislocation, Perthes disease.
• Systemic: RA, gout, haemophilia, sickle cell.
• Obesity, joint infection, avascular necrosis, Paget’s.

🧾 Clinical Features

• Pain ↑ with activity, ↓ with rest.
• Morning stiffness <30 min ⏱️ (if >1 hr → suspect inflammatory arthritis).
• Crepitus + bony enlargement, minimal warmth.
• Deformity: genu varum (bow legs) or valgum (knock knees).
• Hands: Heberden’s (DIP), Bouchard’s (PIP), 1st CMC involvement.
• Reduced range of motion, esp. in hips/knees.

🔎 Investigations

• Bloods: FBC usually normal, ESR/CRP low, RF negative.
• Radiology (“LOSS”):
  • L – Loss of joint space
  • O – Osteophytes
  • S – Subchondral sclerosis
  • S – Subchondral cysts
• MRI/arthroscopy: cartilage loss detail if diagnostic uncertainty.

🩺 Differential Diagnosis

• Age <45 yrs → inflammatory arthritis / trauma.
• Stiffness >1 hr → Rheumatoid arthritis.
• MCP involvement → haemochromatosis.
• Night pain → red flag for malignancy or AVN.
• Multiple tender points → fibromyalgia.

💊 Management

• Lifestyle / Conservative: weight loss, exercise, physio, OT aids, walking sticks, heat packs.
• Pharmacological:
  • 1st line: Paracetamol, topical NSAIDs, capsaicin.
  • 2nd line: Oral NSAIDs/COX-2 inhibitors + PPI cover.
  • 3rd line: Opioids for severe pain (risk/benefit).
  • Intra-articular steroids → 4–6 weeks relief (avoid if infection suspected).
• Non-drug aids: Braces, insoles, TENS.
• Surgery: Hip/knee replacement if conservative measures fail.

🚩 Red Flags

• Night pain or systemic symptoms → suspect malignancy/infection.
• Marked stiffness >1 hr → consider RA.
• Rapidly progressive monoarthritis → urgent review.

✨ Teaching Pearl

OA = “mechanical” arthritis: activity-related pain, short stiffness, bony changes. RA = “inflammatory” arthritis: prolonged stiffness, systemic features, synovitis. Always distinguish the two in exams!

📚 References

• NICE Osteoarthritis in over 16s (NG226)