Classification of Joint Disorders

Noninflammatory (Degenerative joint disorders, osteoarthritis)

• Clear, yellow fluid

• Good viscosity

• WBCs <1000 µL

• Neutrophils <30%

• Similar to blood glucose

Inflammatory (Immunologic disorders, rheumatoid arthritis, systemic lupus erythematosus, scleroderma, polymyositis, ankylosing spondylitis, rheumatic fever, Lyme arthritis)

• Cloudy, yellow fluid

• Poor viscosity

• WBCs 2,000–75,000 µL

• Neutrophils >50%

• Decreased glucose level

• Possible autoantibodies present

Inflammatory (Crystal-induced gout, pseudogout)

• Cloudy or milky fluid

• Low viscosity

• WBCs up to 100,000 µL

• Neutrophils <70%

• Decreased glucose level

• Crystals present

Septic (Microbial infection) ⭐️

• Cloudy, yellow-green fluid

• Variable viscosity

• WBCs 50,000 to 100,000 µL

• Neutrophils >75%

• Decreased glucose level

• Positive culture and Gram stain

Hemorrhagic (Traumatic injury, tumors, hemophilia, other coagulation disorders Anticoagulant overdose)

• Cloudy, red fluid

• Low viscosity

• WBCs equal to blood

• Neutrophils equal to blood

• Normal glucose level