VDR and Hip dysplasia: Since COL2A1 and vitamin D receptor (VDR) are adjacent genes at 12q13 that play a role in chondromorphism and bone mineralization, Granchi et al. reported that SNPs of COL2A1 and VDR genes were associated with DDH-associated OA in the Italian population (Granchi et al., 2002), but SNPs of COL2A1 and VDR genes did not appear to play a role in the association with non-syndromic DDH (Rubini et al., 2008).