A figure showing modulation of the BMP and WNT pathway after mechanical injury in vivo in mice. Modulation of BMP and WNT pathway after mechanical injury in vivo in mice. 7 week old C57BL/6 male mice were challenged in a model of joint surface injury in vivo. In this model the knee joint surface is exposed by medial para-patellar arthrotomy and lateral patellar dislocation. A full thickness injury is made in the patellar groove using a custom made device in which the length of a 26G needle is limited by a glass bead (injured knee), or left uninjured (sham operated control). In either case the patellar dislocation is then reduced and the joint capsule and the skin sutured in separate layers and the mice allowed to walk freely. The animals were killed at different time-points for histological and histochemical analysis. A-B immunohistochemistry for FRZB in sham operated (A) and injured (B) articular cartilage 1 day after the operation. C-D immunohistochemistry for phosphorylated SMAD-1 in sham operated (A) and injured (B) articular cartilage 6 days after the operation. The asterisk indicates the site of injury (occupied by debris). The dashed line indicates the margin of the injury site.