U01.11.036 Osteoarthritis vs rheumatoid arthritis

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Learning Objectives

Differentiate between Osteoarthritis (OA) and Rheumatoid Arthritis (RA) by pathogenesis, clinical presentation, and specific joint involvement. Identify high-yield diagnostic markers like Anti-CCP and Rheumatoid Factor, and recognize the characteristic deformities associated with each condition.

1. Pathogenesis & Predisposing Factors

The fundamental difference between these two conditions lies in whether the primary issue is mechanical “wear and tear” or an autoimmune inflammatory process.

Feature Osteoarthritis (OA) Rheumatoid Arthritis (RA)
Pathogenesis Chronic mechanical stress destroys articular cartilage \rightarrow inflammation with inadequate repair. Autoimmune; proliferative granulation tissue (pannus) erodes cartilage and bone.
Risk Factors Age, obesity, joint trauma, and female sex. Female sex, HLA-DR4 (4-walled “rheum”), smoking.
Markers None (Non-inflammatory). Anti-CCP (highly specific); Rheumatoid Factor (IgM vs IgG Fc).

2. Clinical Presentation

The timing of the pain and the presence of systemic symptoms are the biggest clues in clinical vignettes.

  • Osteoarthritis: Pain in weight-bearing joints after use, improving with rest. Involvement is usually asymmetric. No systemic symptoms.
  • Rheumatoid Arthritis: Morning stiffness lasting > 1 hour, improving with use. Involvement is symmetric. Presents with systemic symptoms (fever, fatigue, weight loss).

3. Joint Findings & Deformities

Condition Radiographic/Joint Findings Specific Deformities
Osteoarthritis Osteophytes (spurs), asymmetric joint space narrowing, and subchondral sclerosis. Heberden nodes (DIP) and Bouchard nodes (PIP).
Rheumatoid Arthritis Erosions, symmetric joint space narrowing, and juxta-articular osteopenia. Ulnar deviation, Swan neck, and Boutonniere deformities. Involves MCP, PIP, and wrist.

Activity:

High-Yield Extra-articular Manifestations (RA):

  • Felty Syndrome: SANTA (Splenomegaly, Anemia, Neutropenia, Thrombocytopenia, Arthritis).
  • Caplan Syndrome: Rheumatoid nodules in the lung + pneumoconiosis.
  • Cervical Subluxation: High risk during intubation!

Activity: