Osteoarthritis (OA) is a disease of synovial joints in which all articular structures are affected. Evidence suggests that a decreased density in the elastic fiber concentration of the knee capsule is associated with joint hypermobility, a condition associated with OA. However, there is no study that shows a direct relationship between the elastic fiber system and knee OA. The purpose of this study is to determine if there is a correlation between the elastic fiber density in medial (MCL) and lateral (LCL) collateral ligaments and the severity of OA. The elastic fiber concentration in MCL and LCL were examined in cadaver knees (n = 10; 4 M, 6 F). The elastic fiber density, measured as the concentration of elastic fibers per unit area, was correlated with the severity of OA, which was graded on a 0-16 scale using histologic and macroscopic markers. Among all subjects, elastic fiber concentrations between MCL (mean 15.49% ± 2.49) and LCL (mean 13.93 ± 3.63) showed a significant difference (P = 0.023). There were no inter-gender differences between the elastic fiber concentration in either MCL or LCL. Among all subjects, the severity of OA was found to be correlated negatively with the elastic fiber concentration in both MCL (r = -0.693, P ≤ 0.05) and LCL (r = -0.718, P ≤ 0.05). This is the first study to show a correlation between the elastic fiber system and knee OA.