The main finding of our study conducted in a cohort of Croatian competing athletes suggested that the TT genotype of TNC rs2104772 T>A and the T-T-T haplotype constructed from COL5A1 rs12722, COL27A1 rs946053 and TNC rs2104772 T>A had a significant association with the risk of developing tendinopathies. This evidence concerns the gene COL5A1 and disease of the tendon.