SMAD3 and osteoarthritis: Stratification analysis of ethnicity found that rs12901499 polymorphism increased the risk of osteoarthritis among both Asians and Caucasians, subgroup analysis by type of osteoarthritis revealed that smad family member 3 gene rs12901499 polymorphism was correlated with the increased risk of hip osteoarthritis, but not associated with knee osteoarthritis.