Mutations in COL9A2 and COL9A3 have previously been linked to human disk disease (Annunen et al., 1999; Paassilta et al., 2001) and studies in transgenic mice have further demonstrated that mutations in collagen IX can lead to disk degeneration but also degenerative joint disease (Kimura et al., 1996). Here, COL9A3 is linked to osteoarthritis.