Age-adjusted D/D+L expressed as a percentage of the dentin control material and the normal articular cartilage control material. The paired t test comparing osteoarthritic (OA) articular cartilage with OA meniscal cartilage was not significant. The analysis of variance result for asparagine + aspartate (Asx), serine (Ser), and leucine (Leu) was P < 0.0001. The Bonferroni post test showed significant differences (P < 0.001) between all three amino acids (Asx, Ser, and Leu). (a) Dentin as control (mean percentage of control + standard deviation). (b) Normal articular cartilage as control (mean percentage of control + standard deviation). Purple represents OA articular cartilage, and pink represents OA meniscal cartilage.