A joint aspirate shows yellow and cloudy fluid with 200–50,000 WBCs and more than 50% PMNs. This fluid is classified as:

A joint aspirate shows yellow and cloudy fluid with 200–50,000 WBCs and more than 50% PMNs. This fluid is classified as:

• A. Septic arthritis
• B. Inflammatory fluid
• C. Non-inflammatory fluid
• D. Normal joint fluid

Answer: (B)

The key idea is how synovial fluid cell counts and the neutrophil differential distinguish types of joint effusions. Inflammatory joint fluids show an elevated white cell count with a predominance of neutrophils, typically in the range of about 2,000–50,000 cells per microliter and more than half of the cells being neutrophils. The fluid is often yellow and cloudy due to the cellular content. Here, the aspirate is yellow and cloudy and has a neutrophil count greater than 50% with a total WBC count that spans into the inflammatory range. That pattern fits inflammatory fluid, which can occur in crystal-induced arthritis, autoimmune inflammatory diseases, or other non-infectious inflammatory processes. It is not normal fluid, which would be clear and have very few cells; and it is not non-inflammatory fluid, which would have a lower WBC count with fewer neutrophils. It’s also not necessarily septic arthritis; septic arthritis typically presents with markedly high WBC counts (often well above 50,000) and purulent fluid with higher risk of positive cultures, though culture results are needed to confirm infection.

The key idea is how synovial fluid cell counts and the neutrophil differential distinguish types of joint effusions. Inflammatory joint fluids show an elevated white cell count with a predominance of neutrophils, typically in the range of about 2,000–50,000 cells per microliter and more than half of the cells being neutrophils. The fluid is often yellow and cloudy due to the cellular content.

Here, the aspirate is yellow and cloudy and has a neutrophil count greater than 50% with a total WBC count that spans into the inflammatory range. That pattern fits inflammatory fluid, which can occur in crystal-induced arthritis, autoimmune inflammatory diseases, or other non-infectious inflammatory processes. It is not normal fluid, which would be clear and have very few cells; and it is not non-inflammatory fluid, which would have a lower WBC count with fewer neutrophils. It’s also not necessarily septic arthritis; septic arthritis typically presents with markedly high WBC counts (often well above 50,000) and purulent fluid with higher risk of positive cultures, though culture results are needed to confirm infection.