Two Genetic Loci Associated with Medial Collateral Ligament Injury Andrew K. Roos, Andrew L. Avins, Marwa A. Ahmed, John P. Kleimeyer, Thomas R. Roos, Michael Fredericson, John P. A. Ioannidis, Jason L. Dragoo, Stuart K. Kim Abstract Background. Medial collateral ligament (MCL) injuries are a common knee injury, especially in competitive athletes. Identifying genetic loci associated with MCL injury could shed light on its etiology. Aim. To identify DNA polymorphisms associated with MCL injury. Methods. A genome-wide association screen was performed using publically available data from the Research Program in Genes, Environment and Health (RPGEH) including 1,572 cases of MCL injury and 100,931 controls. Results. Two SNPs (rs80351309 and rs6083471) showed an association with MCL injury at genome-wide significance (p < 5 x10-8) with moderate effects (Odds Ratios = 2.12 and 1.57, respectively). For rs80351309, the genotypes were imputed with only moderate accuracy, so this SNP should be viewed with caution until its association with MCL injury can be validated. Conclusions. rs80351309 and rs6083471 show a statistically significant association with MCL injury. It will be important to replicate this finding in future studies. Summary Statistics for MCL injury. Summary statistics for 8,668,382 SNPs for Achilles tendinopathy from Roos et al., 2016 (zipped text file, 120 Mb). CHR: chromosom; BP: position in HG18; SNP: rsid; A1: effect allele; P: p-value from fixed effects meta_analysis OR: allelic odds ratio.