What is the diagnostic approach for osteoarthritis?

Diagnosing Osteoarthritis

Imaging is not required to make the diagnosis of osteoarthritis in patients with typical presentation, which includes usage-related pain, short duration morning stiffness, age >40, and symptoms affecting one or a few joints. 1

Clinical Diagnosis

• Osteoarthritis (OA) can be diagnosed primarily through clinical assessment in patients with typical presentation 1
• Clinical hallmarks include:
  • Usage-related joint pain that worsens with activity 1
  • Short duration morning stiffness (typically less than 30 minutes) 1
  • Age over 40 years 1
  • Symptoms affecting one or a few joints 1
  • For hand OA specifically: Heberden and Bouchard nodes and/or bony enlargement with or without deformity affecting characteristic target joints (DIPJs, PIPJs, thumb base, index and middle MCPJs) 1

Diagnostic Algorithm

Step 1: Clinical Assessment

• Evaluate joint pain patterns (usage-related, worse with weight-bearing) 1
• Assess for joint stiffness (typically brief morning stiffness) 1
• Look for characteristic physical findings:
  • Joint line tenderness 2
  • Crepitus with joint movement 2
  • Limited range of motion 2
  • Bony enlargement of affected joints 1
  • Potential joint deformity in advanced cases 2

Step 2: Imaging

• Plain radiographs are the gold standard for morphological assessment when imaging is needed 1

• Imaging is indicated in the following scenarios:

  • Atypical presentations to confirm OA or make alternative diagnoses 1
  • When there is unexpected rapid progression of symptoms 1
  • When there is a change in clinical characteristics suggesting another diagnosis 1

• For knee OA specifically, weight-bearing and patellofemoral views are recommended for optimal detection 1

• Classical radiographic features include:

  • Joint space narrowing 1
  • Osteophytes 1
  • Subchondral bone sclerosis 1
  • Subchondral cysts 1
  • In erosive OA: subchondral erosion 1

Step 3: Laboratory Testing

• Blood tests are not required for diagnosis of typical OA but may be needed to exclude coexistent disease 1
• Consider laboratory testing when:
  • Patient has marked inflammatory symptoms/signs 1
  • Symptoms involve atypical sites 1
  • There is suspicion of an inflammatory arthritis 1
  • ESR, RF, and CRP are usually normal or only mildly elevated in non-erosive OA 1

Step 4: Advanced Imaging

• MRI is not routinely needed but may be considered when:
  • Plain radiographs are normal but clinical suspicion remains high 1
  • More accurate cartilage assessment is needed 1
  • There is need to evaluate for concomitant soft tissue pathology 1

Special Considerations

• Erosive OA is a specific subgroup with worse clinical and structural outcomes, characterized by:

  • Abrupt onset 1
  • Marked pain and functional impairment 1
  • Inflammatory symptoms and signs (stiffness, soft tissue swelling, erythema) 1
  • Mildly elevated CRP levels 1
  • Radiographic subchondral erosion 1

• Differential diagnosis to consider:

  • For hand OA: psoriatic arthritis, rheumatoid arthritis, gout, and hemochromatosis 1
  • For knee OA: meniscal pathology, anterior cruciate ligament injury, other crystal arthropathies 1, 2

Common Pitfalls to Avoid

• Relying solely on radiographic findings without clinical correlation - imaging abnormalities of OA are common with increasing age and may not correlate with symptoms 1
• Assuming all joint pain in older adults is due to OA without considering other diagnoses 1
• Missing inflammatory arthritis by not obtaining appropriate laboratory tests when presentation is atypical 1
• Failing to recognize that functional impairment in hand OA can be as severe as in rheumatoid arthritis 1
• Overlooking that patients with polyarticular hand OA are at increased risk of knee OA, hip OA, and OA at other sites 1