Intraarticular injection of FGF8 induced the sulfated glycosaminoglycan release in knee joints and destruction of patella. Fifty micrograms of FGF8 was injected into the knee joint of rats (vehicle). KM1334 (the anti-FGF8 antibody (Ab)) was intraperitoneally administered before the injection of FGF8. For the saline injection group (saline), 50 μl sterile saline was injected into the knee joint. Synovial lavage was performed with saline 3 days after the FGF8 injection. (a) Sulfated glycosaminoglycan (S-GAG) content in the synovial lavage fluid was measured by the 1,9-dimethylmethylene blue method. (b) The cartilaginous portion of the patella was digested with papain to measure the weight of the residual bone. Each column represents the mean ± standard error (n = 5). ###P < 0.001 compared with the saline group (Student's t test), *P < 0.05 compared with the vehicle group (Aspin–Welch test).