Boer CG, Yau MS, Rice SJ, et al. - This study was carried out to evaluate whether the genome-wide association of phenotypes based on clustering patterns of hand osteoarthritis identifies _WNT9A as a novel osteoarthritis gene. Researchers applied data from the Rotterdam Study (RSI, RSII, and RSIII) to create three hand osteoarthritis (OA) phenotypes based on clustering patterns of radiographic OA severity to increase power in our modest discovery genome-wide association studies in the RS (n=8700), and sought replication in an independent cohort, the Framingham Heart Study (n=1203). They applied multiple approaches that leverage different levels of information and functional data to further evaluate the underlying biological mechanisms and candidate genes for replicated loci. A robust novel genetic locus was distinguished for hand OA on chromosome 1, of which _WNT9A is the most likely causal gene. It has been reported that multiple genetic loci were distinguished to be correlated with OA across multiple joints. This research validates the potential for novel insight into the genetic architecture of OA by applying biologically meaningful stratified phenotypes.