Comparison of synovial fluid cartilage marker concentrations and chondral damage assessed arthroscopically in acute knee injury

Objective: To examine the correlation between synovial fluid cartilage markers and degree of cartilage damage determined by arthroscopic evaluation in subjects with acute knee injury. Design: Chondral damage was quantified using a validated arthroscopic scoring system in 20 subjects with effusive acute knee injuries of less then 4 months duration and no history or radiographic evidence of joint pathology. Levels of synovial fluid 3B3(-) neoepitope, 3B3(+) chondroitinase generated epitope of proteoglycan, keratan sulfate (KS) and hyaluronic acid (HA) were measured by competitive enzyme-linked immunosorbent assays using monoclonal antibodies 3B3 and 5D4. Total sulfated glycosaminoglycan (GAG) was measured by 1,9-dimethylmethylene blue colorimetric dye-binding assay. Results: We found a dramatic decrease in levels of 3B3(-) (r(s) = -0.62, P = 0.004), and GAG (r(s) = -0.49, P = 0.03) with increasing chondral damage score; but no correlation of damage score with 3B3(+), KS or HA levels. Conclusion: These data reveal a change in cartilage metabolism within the first 4 months of symptomatic knee injury evinced by a significant inverse correlation of 3B3(-) and GAG levels to chondral lesion severity. These results suggest that serial measurement of these synovial fluid markers in the setting of acute knee injury could predict chondral lesion severity and aid in the decision to intervene surgically.