Statin treatment increases the clinical risk of tendinopathy through matrix metalloproteinase release - a cohort study design combined with an experimental study.

Recent experimental evidence indicates potential adverse effects of statin treatment on tendons but previous clinical studies are few and inconclusive. The aims of our study were, first, to determine whether statin use in a cohort design is associated with tendinopathy disorders, and second, to experimentally understand the pathogenesis of statin induced tendinopathy. We studied association between statin use and different tendon injuries in two population-based Swedish cohorts by time-dependent Cox regression analysis. Additionally, we tested simvastatin in a 3D cell culture model with human tenocytes. Compared with never-users, current users of statins had a higher incidence of trigger finger with adjusted hazard ratios (aHRs) of 1.50 for men (95% confidence interval [CI] 1.21-1.85) and 1.21 (1.02-1.43) for women. We also found a higher incidence of shoulder tendinopathy in both men (aHR 1.43; 1.24-1.65) and women (aHR 1.41; 0.97-2.05). Former users did not confer a higher risk of tendinopathies. In vitro experiments revealed an increased release of matrix metalloproteinase (MMP)-1 and MMP-13 and a weaker, disrupted matrix after simvastatin exposure. Current statin use seems to increase the risk of trigger finger and shoulder tendinopathy, possibly through increased MMP release, and subsequently, a weakened tendon matrix which will be more prone to injuries.