Osteoarthritis

Etiology

• Risk Factors
  • Age: Most significant risk factor.
  • Obesity: Increases mechanical stress on weight-bearing joints (knees, hips).
  • Female gender: More common in women, especially post-menopause.
  • Joint Trauma/Overuse: Previous injuries or occupations with repetitive stress can predispose to OA.
  • Genetics: A family history plays a role, particularly in OA of the hand and hip.

Differential diagnosis

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• Traditionally, osteoarthritis (OA) has been classified as a non-inflammatory or “wear-and-tear” arthritis
  • The inflammation is generally less pronounced
  • It doesn’t typically feature systemic inflammation markers
  • It doesn’t involve autoimmune mechanisms as its primary cause
  • Morning stiffness is typically shorter in duration

Osteoarthritis (OA) vs Rheumatoid Arthritis (RA)

Feature	Osteoarthritis (OA)	Rheumatoid Arthritis (RA)
Mechanism	Mechanical “Wear & Tear”	Autoimmune (Pannus)
Stiffness	< 30 min (Worse w/ use)	> 1 hr (Better w/ use)
Symmetry	Asymmetric	Symmetric
Key Joints	DIP (Heberden), PIP, Knees	MCP, PIP, Wrist (Spares DIP)
Labs	Normal	+Anti-CCP (Specific), +RF, ↑ ESR
X-ray	Osteophytes, Sclerosis	Marginal Erosions, Osteopenia
Treatment	NSAIDs, Acetaminophen	DMARDs (Methotrexate)

1. Stiffness

• OA (<30m): “Gelling.” Synovial fluid gets thick at rest. Movement quickly warms and lubricates it.
• RA (>1h): Edema. Inflammatory fluid pools during sleep. Takes time to mechanically pump/drain the boggy joint.

2. Pain

• OA (Worse w/ use): Mechanical. Bone-on-bone friction compresses exposed nerve endings.
• RA (Better w/ use): Washout. Movement flushes out stagnant inflammatory cytokines and fluid, relieving pressure.

3. Pathology

• OA (Osteophytes): Construction. Bone grows spurs to widen surface area and stabilize the failing joint.
• RA (Erosions): Destruction. Pannus (granulation tissue) releases enzymes/RANKL that eat into the bone.

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Treatment

Approach

Follow a stepwise approach to treatment: Start with nonpharmacological management, followed by pharmacological and/or surgical treatment if needed.

• Nonpharmacological management: e.g., exercise and weight loss
• Pharmacotherapy
  • First line: e.g., topical or oral NSAIDs
  • Second line: e.g., acetaminophen or intraarticular glucocorticoid injections
• Surgical management: e.g., complete or partial joint replacement (arthroplasty) using an endoprosthesis

Tip

Pharmacotherapy should only be used as a short-term treatment in symptomatic patients; long-term therapy is associated with many adverse effects.