Kizawa et al. (2005) found a significant association between osteoarthritis of the knee and hip and a polymorphism in the aspartic acid repeat in the N-terminal region of the ASPN protein (608135.0001). The aspartic acid repeat polymorphism inhibits ... Kizawa et al. (2005) found a significant association between osteoarthritis of the knee and hip and a polymorphism in the aspartic acid repeat in the N-terminal region of the ASPN protein (608135.0001). The aspartic acid repeat polymorphism inhibits chondrogenesis and increases susceptibility to osteoarthritis. Asporin is an extracellular matrix component expressed abundantly in the articular cartilage of individuals with osteoarthritis. Jiang et al. (2006) genotyped the aspartic acid repeat in the ASPN gene in 218 Han Chinese with radiographically confirmed symptomatic knee osteoarthritis and 454 age-matched controls and found that the D14 allele was significantly overrepresented in knee osteoarthritis patients (p = 0.0063 after Bonferroni correction; odds ratio, 2.04). D14 was more frequent in early-onset patients, and the age at onset in patients with D14 was earlier.