The overall research goal of this NSF CAREER project was to characterize mechanical failures in the human meniscus, a soft fibrous tissue in the knee. Meniscal tears are a debilitating and prevalent injury, accounting for over 500,000 U.S. hospital visits per year. Unfortunately, there are limited treatment options for this injury, and efforts to prevent meniscal tears are hindered by a lack of knowledge on the physical mechanisms that cause failure in young and older individuals. This project has addressed this knowledge deficiency by using novel experimental, theoretical and computational approaches to determine how single and repeated loads can cause failure and how aging influences this behavior. The INTELLECTUAL MERIT of this project is that we have gained a fundamental understanding of failure mechanisms in soft fibrous tissue. This includes using experiments to calculate the mechanical properties that define the ability of the human meniscus to resist single large loads (static failure) and repeated smaller loads (fatigue). We also developed and validated computational models that could simulate this experimental failure behavior. Notably, we found that older menisci were generally weaker and more susceptible to tearing from high-magnitude loads, but older and young menisci were equally resistant to tears at low-magnitude loads. We also found that continuum damage mechanics was an appropriate theory to model failures caused by static and fatigue loads. In total, this project resulted in 12 journal articles and 22 conference proceedings. This research has BROADER IMPACTS on engineering and health care technology. The findings from this study can help identify physical activities that are high-risk for knee injury, and thereby transform efforts to prevent meniscus injuries. Moreover, the models used to predict soft tissue tears give researchers and clinicians a powerful tool to visualize tissue failure and efficiently test new prevention strategies and treatments. These models are also applicable to non-biological soft materials and fiber composites. New technology developed from this project includes the device Print-A-Punch and the web application Dots-on-Plots, which are both free to the public. This project helped train 7 graduate students and 12 undergraduate students who are now working as engineers or are pursuing higher graduate degrees in engineering. The findings from this study have enhanced educational materials in undergraduate and graduate classes by giving visual learners an ability to see the application of material failure in a relevant manner (knee injury), and have been presented to K-12 students to teach them about safe practices to protect joints.

Last Modified: 06/28/2022
Modified by: Trevor Lujan