Figure 4. Osteophytes in asj-2J mice at 12 weeks of age display AP (pink) and TRAP (yellow) activities in the lateral collateral ligament in the knee (a) and the supraspinatus tendon in the shoulder (b).

AP positive fibrocartilage cells (green arrows) were seen in the unmineralized regions (non-CB) of the shoulder osteophyte and in the less mature knee osteophyte. The shoulder osteophyte was more mature with TRAP positive osteoclasts (yellow arrows) and AP positive osteoblasts (pink arrows) lining the bone surfaces in the interior of the osteophyte. T Blue, Toluidine Blue O stain; AP, alkaline phosphatase; TRAP, tartrate-resistant acid phosphatase; CB, Calcein Blue stain for mineral. Scale bar = 200μm.