Differences in mean total amino acids D+L (nmol/mg + standard deviation) between normal articular cartilage (n = 12 age-matched samples), paired osteoarthritic (OA) articular cartilages (n = 30), and OA meniscal cartilages (n = 30). The normal tissue was age-matched to the OA tissues. Analysis of variance results were P < 0.0001 for asparagine + aspartate (Asx), glutamate + glutamine (Glx), serine (Ser), and alanine (Ala); P < 0.0005 for leucine (Leu); and P = 0.0012 for isoleucine (Ile). Significance of change from normal cartilage by Bonferroni post test was *P < 0.01 and **P < 0.001. Light blue represents normal articular cartilage, purple represents OA articular cartilage, and pink represents OA meniscal cartilage.