Osteoarthritis

Pathophysiology - Wear and Tear Blues

• Primarily a degenerative, “wear and tear” process leading to joint failure, distinct from the autoimmune inflammation of rheumatoid arthritis.
• Articular Cartilage Breakdown:
  • Initial injury or stress triggers chondrocyte dysfunction.
  • Chondrocytes release degradative enzymes (e.g., metalloproteinases).
  • Results in loss of proteoglycans and collagen, causing cartilage to soften, fissure, and erode.
• Subchondral Bone Remodeling:
  • Underlying bone thickens (sclerosis).
  • Osteophytes (bone spurs) form at the joint margins.

⭐ Unlike inflammatory arthritis, osteoarthritis typically shows normal Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) levels.

Clinical Presentation - Grumpy, Creaky Joints

• Onset: Insidious, typically asymmetrical.
• Pain: Deep, achy; worsens with activity/weight-bearing, improves with rest.
• Stiffness: Morning stiffness is brief (< 30 minutes); may experience gelling (stiffness after inactivity).
• Exam: Crepitus, limited range of motion, bony enlargements (osteophytes).
  • Heberden's nodes: Distal interphalangeal (DIP) joints.
  • Bouchard's nodes: Proximal interphalangeal (PIP) joints.
• Systemic: No constitutional symptoms (e.g., fever, fatigue, weight loss).

⭐ The brief duration of morning stiffness (< 30 min) is a key feature distinguishing OA from inflammatory arthritides like Rheumatoid Arthritis (> 60 min).

Diagnosis - The Joint Detective

• Primarily Clinical: Diagnosis is based on age, usage history, and exam findings (e.g., crepitus, bony enlargement). Morning stiffness is typically brief (< 30 minutes).
• Imaging (X-ray):
  • 📌 JOSS Mnemonic:
    • Joint space narrowing (asymmetric)
    • Osteophytes
    • Subchondral sclerosis
    • Subchondral cysts
• Labs: Normal ESR/CRP, negative RF/anti-CCP.
• Arthrocentesis: Non-inflammatory synovial fluid (WBC < 2,000/mm³).

⭐ Exam Favourite: X-ray findings often correlate poorly with patient symptoms; treat the patient, not the X-ray.

Management - Soothing the Squeak

• Goal: Control pain, improve function, and slow joint damage using a stepwise approach, starting with conservative measures.

⭐ Weight loss is the most effective non-pharmacologic intervention for reducing pain and disability in knee OA.

High‑Yield Points - ⚡ Biggest Takeaways

• Degenerative "wear-and-tear" arthritis due to progressive cartilage loss, not an autoimmune process.
• Key symptom: morning stiffness lasting < 30 minutes that worsens with use throughout the day.
• Affects DIP (Heberden's nodes) and PIP (Bouchard's nodes); characteristically spares the MCP joints.
• Classic X-ray findings: asymmetric joint space narrowing, osteophytes, subchondral sclerosis, and cysts.
• Diagnosis is clinical; inflammatory markers (ESR, CRP) and RF are normal.
• Management: weight loss, physical therapy, then acetaminophen and NSAIDs.