Aspiration yields yellow, transparent fluid with 200–2000 WBCs and less than 25% PMNs. This fluid is best classified as:

Aspiration yields yellow, transparent fluid with 200–2000 WBCs and less than 25% PMNs. This fluid is best classified as:

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

Answer: (A)

The key concept here is how synovial fluid analysis distinguishes types of joint effusions by cell count and the neutrophil proportion. Normal or non-inflammatory joints have clear or pale-yellow fluid with very low leukocyte counts and a small neutrophil fraction. In non-inflammatory effusions, the WBC count is higher than normal but still modest (roughly 200–2,000 cells per microliter) and neutrophils remain a minority, usually less than 25%. In contrast, inflammatory effusions show WBCs in the thousands to tens of thousands with neutrophils often exceeding 50%, and septic arthritis typically has very high WBCs (often >50,000) with a predominance of neutrophils and sometimes purulent fluid. Given yellow, transparent fluid with 200–2000 WBCs and less than 25% PMNs, this fits the non-inflammatory pattern. The appearance aligns with a non-inflammatory process, whereas higher WBC counts with a high neutrophil percentage would point toward inflammatory or septic etiologies.

The key concept here is how synovial fluid analysis distinguishes types of joint effusions by cell count and the neutrophil proportion. Normal or non-inflammatory joints have clear or pale-yellow fluid with very low leukocyte counts and a small neutrophil fraction. In non-inflammatory effusions, the WBC count is higher than normal but still modest (roughly 200–2,000 cells per microliter) and neutrophils remain a minority, usually less than 25%. In contrast, inflammatory effusions show WBCs in the thousands to tens of thousands with neutrophils often exceeding 50%, and septic arthritis typically has very high WBCs (often >50,000) with a predominance of neutrophils and sometimes purulent fluid.

Given yellow, transparent fluid with 200–2000 WBCs and less than 25% PMNs, this fits the non-inflammatory pattern. The appearance aligns with a non-inflammatory process, whereas higher WBC counts with a high neutrophil percentage would point toward inflammatory or septic etiologies.