Unraveling the Distinction Between Healthy and Harmful Tendon Impingement

University Of Rochester, Rochester NY

Investigators

Abstract

Tendons connect muscles to bones and experience stretching forces when muscles contract. Many tendons also encounter compressive forces from physical contact with bone, a phenomenon known as “impingement.” While impingement is common in healthy tendons, tendon diseases often develop at sites of tendon impingement. Unfortunately, it is not known why impingement is typically benign yet sometimes harmful. Preliminary studies suggest that the speed of impingement could influence its effect on tendon. That is, while fast impingement produces large deformations in tendon cells and their surrounding structures, slow impingement produces smaller deformations and squeezes substantial amounts of water out of tendons. Importantly, this water loss could protect tendons from future episodes of impingement, much like a deflated balloon is harder to pop than a full one. Thus, the hypothesis for this research is that while fast impingement damages tendon health, slow impingement is not only less harmful but also protects tendon from later bouts of fast impingement. Since impingement has been linked to several painful tendon diseases, the findings of this study could one day impact clinical care for musculoskeletal disorders. In addition, this study will impact the greater Rochester community, as it will be carried out in tandem with the PI’s long-running summer research program for Rochester City School District high school students; and coursework that prepares graduate students to communicate science and engineering clearly to broad audiences. This project seeks to determine why a routine occurrence – physical contact between tendon and bone (i.e., “impingement”) – occasionally triggers a pathological response. To this end, the objectives of this research are to investigate whether the effects of impingement on tendon health are modulated by impingement speed and to test whether prior exposure to slow impingement protects tendon from rapid impingement. The experiments will be conducted using innovative multiscale experimental and computational methods that other biomechanics and mechanobiology researchers can adopt to advance their own work. Moreover, data will be acquired that could shed light on key unresolved questions, including why musculoskeletal pain is often worst in the morning before diminishing as the day progresses. Specifically, this work is expected to demonstrate that musculoskeletal tissues are especially vulnerable to impingement when they have not been recently loaded (e.g., in the morning). However, early joint movements expel water from the tendon, and this loss of fluid is protective against future impingement episodes (much like deflated balloons are difficult to pop). This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.