Articular cartilage is a load-bearing and low-friction soft tissue in the knee joint (Athanasiou et al., 1991, Soltz and Ateshian, 2000). The constituents of cartilage include collagens, proteoglycans (PG), and water (Chen et al., 2001). The structural and mechanical properties of normal articulating joint cartilage are known to show site-specific variation (Hamsayeh Abbasi Niasar, 2023, Mäkelä et al., 2014). Osteoarthritis (OA) is a disease that alters the structure and composition of human cartilage (Setton et al., 1994a). The site-specific variation in cartilage mechanical properties may influence the initiation and progression of OA in individual joint sites (Froimson et al., 1997).

While OA-associated changes in cartilage mechanical properties have been shown earlier for human tibial, femoral, and patellar cartilage (Ebrahimi et al., 2021, Ebrahimi et al., 2019, Nissinen et al., 2021), each site was studied independently in different cadaver joints. Thus, those may not well represent the interaction between different joint cartilage sites in a single human knee. Moreover, several factors, including age and activity level, may lead to differences in cartilage properties between subjects (Kempson., 1982). Determining the site-specific mechanical properties from donor-matched samples might facilitate a better understanding of OA initiation and progression.

This study aims to compare the site-specific changes in elastic and viscoelastic mechanical properties of human cartilage during OA. In this study, cartilage samples from different anatomical sites were extracted from the same batch of cadavers to better reflect the interaction between joint sites and the mechanical environment within the human knee. We hypothesize that because cartilage in different knee joint sites experiences different strains and stresses, cartilage mechanical properties in these sites are adapted to the corresponding mechanical environment and the change in the mechanical properties during OA are also site-specific.