Osteoarthritis

Snapshot

• A 56-year-old woman presents to her primary care physician with pain in her hands. The pain began approximately 1 year prior to presentation and has progressively worsened. She describes the pain being worse in the evening and improves in the morning. She has also noticed swelling in her knuckles. On physical exam, there is bone deformity noted on the distal and proximal interphalangeal joints, as well as tenderness upon palpation of the affected joints.

Introduction

• Clinical definition 
  • a degenerative disorder affecting the articular cartilage
• Epidemiology
  • incidence
    • most common articular disease
  • demographics
    • more common in women and the elderly
  • risk factors
    • modifiable
      • obesity
      • trauma
      • repetitive use (e.g., heavy labor)
    • non-modifiable
      • age
      • female gender
      • family history
• Pathogenesis
  • not completely understood but is more complex than “wear and tear” of the joint and inflammation appears to be involved
    • chondrocytes attempt to proliferate and synthesize proteoglycans when it is injured
      • however, degradation exceeds synthesis, thus compromising the extracellular matrix
    • inflammatory processes appear to promote proteolytic articular degeneration mediated by chondrocytes
      • e.g., transforming growth factor-β (TGF-β) induces chondrocytes to secrete matrix metalloproteinase (MMPs) to degrade type II collagen
  • eventually portions of the articular cartilage and subchondral bone is sloughed off into the joint space (synovial space)
    • forming loose bodies (joint mice)
  • subchondral bone becomes exposed and rubs on the adjacent bone, resulting in
    • bone eburnation (polished ivory)
  • osteophytes (bony outgrowths) develop due to bone remodeling
    • can be appreciated in the
      • distal interphalangeal joint as Herberden nodes
      • proximal interphalangeal joint as Bouchard nodes
  • late stage osteoarthritis is characterized by loss of chondrocytes and degraded extracellular matrix
• Prognosis
• favorable with joint replacement

Biology and Anatomy

• Articular cartilage greatly decreases friction with movement and resists tension and compressive forces
  • composed of type II collagen and proteoglycans which are synthesized and secreted by chondrocytes
• chondrocytes maintain cartilage with its anabolic and catabolic activities

Presentation

• Symptoms 
  • pain
    • worsens with use and improves with rest
    • commonly involves the hands, hips, and knees
• Physical exam
  • joint tenderness
  • decreased range of motion
  • bony swelling
    • swelling of the distal interphalangeal (Herberden nodes) 
• swelling of the proximal interphalangeal (Bouchard nodes)

Imaging

• Radiography
  • indication
    • may be used to confirm the diagnosis and determine disease progression and severity
  • findings 
    • joint space narrowing 
    • osteophytes 
    • joint mice
• subchondral sclerosis

Studies

• Labs
  • c-reative protein (CRP) and erythrocyte sedimentation rate (ESR) levels are normal
• Diagnostic criteria
• typically a clinical diagnosis

Differential

• Rheumatoid arthritis
• Arthralgia
• Bursitis 
  • localized tenderness to palpation without radiographic changes
  • treat with NSAIDs
• Tendonitis
  • greater trochanter pain syndrome 
    • iliotibial band dysfunction
• gluteus medius/minimus

Treatment

• Conservative
  • exercise and weight loss
    • indication
      • first-line in the management of osteoarthritis
• Medical
  • topical or oral nonsteroidal antiinflammatory drugs (NSAIDs)
    • indication
      • for the symptomatic management of osteoarthritis in patients who do not adequately respond to conservative treatment
• Operative
  • orthopedic surgery
    • indication
• in patients with advanced pain who are unresponsive to conservative and pharmacologic therapy

Complications

• Pain
• Bone deformity
• Functional impairment