Association of synovial fluid analytes and osteoarthritis severity. Association of synovial fluid (a) isomerized aspartate (IsoAsp), (b) protein, and (c) glycosaminoglycan (GAG) with the modified Mankin scores of lesional cartilage. Analytes were natural logarithm (LN)-transformed to produce a normal distribution as determined by the D'Agostino and Pearson omnibus normality test. Results represent 10 separate individual patients for whom both cartilage and synovial fluid were available (Table 1). NS, not significant; SF, synovial fluid.