In addition, mice lacking Bmp2 in the limb element showed early postnatal fibrotic degeneration of the articular cartilage [28], while loss of Bmpr1a in the articular regions in mice showed defective joint formation and accelerated wearing of the articular cartilage with age, thereby resembling human osteoarthritis [29]. The gene discussed is BMPR1A; the disease is osteoarthritis.