Higher strains in the inner region of the meniscus indicate a potential source for degeneration

Complex structural properties of menisci can be characterized in part by their inhomogeneous strain response under compression. This pilot study explored the feasibility to quantify characteristic strain distributions on meniscus cross-sections subjected to static compression using electronic speckle pattern interferometry (ESPI). Cross-sectional specimens of 5-mm thickness were harvested from eight human menisci. After application of 20% pre-strain, strain maps in response to 10μm compression were captured with ESPI. The 10μm compression induced an aggregate strain of nominally 0.14% and resulted in highly non-uniform strain distributions. Local compressive strain captured by ESPI ranged from 0.03% to 0.7%. The highest strain was in the central region of meniscus cross-sections, and the lowest magnitude of strain was at the femoral surface of the meniscus. After stratifying for age, peak compressive strain in older menisci (71±6 years, n=4) was 0.33%±0.09, compared to 0.25%±0.06 in younger menisci (34±9 years, n=4). In conclusion, this study captured for the first time continuous strain distribution maps over entire meniscus cross-sections. The non-uniform strain distributions demonstrated inhomogeneous structural properties. Age-related differences in characteristic strain distributions likely represent degenerative changes. As such, ESPI provides a novel strategy of further characterize meniscal function and degeneration.