| Paraclinical test | Susceptible etiology | Result | |
| CBC, ESR, CRP | Infection, Inflammation, and rheumatologic disease | Increased WBC and platelet, elevated ESR and CRP | |
| Malignancy | Increased WBC OR cytopenia, elevated ESR and CRP | ||
| Synovial fluid analysis and culture | Septic arthritis | Turbid appearance, WBC > 50,000 - 100,000, PMNs > 75%, positive culture | |
| Transient synovitis | Clear yellow appearance, WBC = 5000 - 15,000, PMNs < 25%, negative culture | ||
| Cultures | Urethra, Cervix, Rectus, and Pharynges | Gonococcal arthritis | Neisseria gonorrhoeae |
| Urine and stool | Reactive arthritis | Chlamydia in U/C, Salmonella, Shigella, Campylobacter and Yersinia in S/C | |
| Blood | Hematogenous Infection | S. aureus, Haemophilus influenzae | |
| Bone | Osteomyelitis | S. aureus, Pseudomonas, or other microorganisms | |
| Throat | Acute rheumatic fever | Hemolytic Streptococci Group A | |
| ASO Titer | Acute rheumatic fever | Increased level of ASO titer | |
| Lyme Titer | Lyme disease | Positive | |
| ANA Test | systemic lupus erythematosus | Positive (1:80 or higher) | |
| Coagulation profile | Hemarthrosis, Known hemophilia | Increased aPTT | |