<unk>  should be considered whenever a person has rapid onset pain in a swollen joint, regardless of fever. One or multiple joints can be affected at the<unk> me time. Laboratory studies such as blood cultures, white blood cell count with differential, ESR, and CRP should also be included. However, white cell count, ESR, and CRP are nonspecific and could be elevated due to infection elsewhere in the body. Serologic studies should be done if lyme disease is suspected. Blood cultures can be positive in 25 to 50% of those with<unk>  due to spread of infection from the blood. CRP more than 20 mg/L and ESR greater than 20 mm/hour together with typical signs and symptoms of<unk>  should prompt arthrocentesis from the affected joint for synovial fluid examination. The synovial fluid should be collected before the administration of antibiotics and should be sent for gram stain, culture, leukocyte count with differential, and crystal studies. This can include NAAT testing for N. gonorrhoeae if suspected in a sexually active person. In children, the Kocher criteria is used for diagnosis of<unk> .
Septic arthritis
Osteoarthritis
Knee arthritis
Gout
Compression arthralgia
Rheumatoid arthritis
Inflammatory arthritis
Reactive arthritis