(A) RNA was collected from knee cartilage of 12-week-old Aggrecan-CreERT2;Klf2flox/flox (cKO) and littermate control mice 2 weeks after tamoxifen injection (n=14 per group). mRNA levels are relative to cKO for Cre, and relative to control for Klf2. *P<0.05, unpaired Welch’s t-test. (B) Sixteen-week-old cKO and littermate control mice underwent DMM or sham surgery 2 weeks after tamoxifen injection. The knees were harvested at 8 weeks postoperatively for histological analysis (n=8 per group). (C) Representative Safranin-O staining images of control and cKO mice with DMM surgery. Scale bars, 200 µm. (D) Summed Osteoarthritis Research Society International (OARSI) scores for the medial femoral condyle and tibial plateau. (E) Meniscus histopathological scores. (F) Synovitis scores. For (D–F), *P<0.05, Sidak’s multiple comparison test. All quantitative data are expressed as means±SE, and results of two-way ANOVA test are shown in supplementary table 2.