Group I: Noninflammatory
(200-300 WBC, < 25% PMNs)
- Osteoarthritis
- Trauma (may be hemorrhagic)
- Osteochondritis dissecans
- Osteochondromatosis
- Neuropathic arthropathy (may be hemorrhagic)
- Subsiding or early inflammation
- Hypertrophic osteoarthropathy (group I or II)
- Pigmented villonodular synovitis (may be hemorrhagic)
Group II: Inflammatory
(3000-50,000 WBC, >50% PMNs)
- Rheumatoid arthritis
- Gout or pseudogout
- Reactive arthritis (Reiter’s syndrome)
- Ankylosing spondylitis
- Psoriatic arthritis
- Arthritis accompanying inflammatory bowel disease
- Rheumatic fever (group I or II)
- Systemic lupus erythematosus (group I or II)
- Scleroderma (group I or II)
- Tuberculosis
- Mycotic infection
Group III: Purulent
(>50,000 WBC, >75% PMNs)
- Pyogenic bacterial infection
Hemorrhagic
- Hemophilia or other bleeding disorder
- Trauma with or without fracture
- Neuropathic arthropathy
- Pigmented villonodular synovitis
- Synovioma
- Hemangioma and other benign neoplasms