Sox9, Runx2, and Scleraxis expression. (A-D) Sox9; (E-H) Runx2; (I-L) Scleraxis. (A,E,I) ACL from normal knee; (B,F,J) ACL from aging knee; (C,G,K) fibroblast-like cell aggregates in the degenerated ACL. (D,H,L) Chondrocyte-like cell aggregates in the degenerated ACL. Black arrows, positive cells; white arrows, negative cells. (Original magnification ×40). The graph (M) represents the percentage (mean ± SEM) of Sox9-, Runx2-, and Scleraxis-positive cells. **P < 0.01.