Investigations in Rheumatology

 

• Interpreting bone or joint X-rays

  DOCS.

  Density:

  • ↑ = sclerosis.
  • ↓ = osteopenia.

  Bone Outline:

  • Joint space narrowing: uneven/asymmetrical in OA, even/symmetrical in RA.
  • Lesions: erosions (holes), cysts (holes with intact edges), and osteophytes (growths seen at edge).
  • Periosteal reaction: new bone post-trauma.

  Cortex and medulla:

  • Cortical thickening.
  • Trabecular pattern.
  • Bone lesions.

  Soft tissue:

  • Swelling

• Joint aspiration

  Definition

  • Aspiration of synovial fluid for culture and light microscopy (looking for crystals).

  Indications

  • Acute monoarthritis.
  • Chronic arthritis.
  • Symptom relief in grossly-swollen joints.

  Results

  • Normal joint: clear fluid, normal viscosity, <200 WBC/mm3, no neutrophils.
  • Osteoarthritis: clear or yellow fluid, ↑viscosity, <1000 WBC/mm3, 25% neutrophils.
  • Haemorrhagic: bloody, viscosity variable, 200-2,000 WBC/mm3, 50% neutrophils.
  • Crystal arthritis: turbid yellow fluid, ↓viscosity, 50-5,000 WBC/mm3, 50% neutrophils.
  • RA: turbid yellow fluid, ↓viscosity, 2,000-100,000 WBC/mm3, >50% neutrophils.
  • Septic arthritis: turbid yellow fluid, ↓viscosity, 10,000-100,000 WBC/mm3, >75% neutrophils.