We found that the joint space was increased by 44% (P < 0.05), and the Osteoarthritis Research Society International (OARSI) score was increased by 270% (P < 0.01) in the cKO mice compared to control mice (Fig. 3F,G), suggesting that a lack of Phd2 may increase the risk of osteoarthritis development. This evidence concerns the gene EGLN1 and osteoarthritis.