Elevated HTRA1 expression is associated with AMD, arthritis, Alzheimer's disease, and Duchenne muscular dystrophy (Bakay, Zhao, Chen, & Hoffman, 2002; Gibbs et al., 2008; Hu et al., 1998; Tsuchiya et al., 2005; Yang et al., 2006). Here, HTRA1 is linked to arthritic joint disease.