The cervical spine ligaments, including the anterior longitudinal ligament (ALL) and posterior longitudinal ligament (PLL), play a key role in maintaining spinal stability by limiting excessive movements. This study investigates how ageing affects the mechanical properties of these ligaments. We analysed 33 samples from 12 human cervical spines (15 ALL, 18 PLL), averaging data from the same donors for independent analysis, resulting in 18 final samples (8 ALL, 10 PLL). To explore age-related changes, we classified the samples into two groups—below and above 50 years old—aligning with the peak incidence of major musculoskeletal disorders. The investigation concentrated on the effects of age on four mechanical parameters of the uniaxial stress–stretch curve: initial tangent stiffness ($E_0$), maximum tangent stiffness ($E_m$), ultimate stress ($P_u$) and ultimate stretch (${\lambda }_u$). When the age effect is neglected, then the behaviours of both the ALL and PLL appeared similar. However, when introducing age as a variable into the context of the ALL and PLL, statistically significant differences became evident. The findings underscored a reduction in maximum tangent stiffness (p-value = 0.0147), ultimate stress (p-value = 0.0009), and ultimate stretch (p-value = 0.0024) when the ALL and PLL were grouped under and above 50 years as a consequence of ageing.

The Lateral Collateral Ligament (LCL), one of the four major ligaments in the knee joint, resides on the outer aspect of the knee. It forms a vital connection between the femur and the fibula. The LCL’s primary role is to provide stability against Varus forces, safeguarding the knee from undue rotation and tibial displacement. Uniaxial mechanical testing was conducted on the dog bone (DB) samples in this study. The porcine of different ages, from 3 months to 48 months (4 years) old, were used to analyse the effect of age. A constant head speed of 200 mm/s was applied throughout the tests to mimic strain–stress and damage responses at an initial strain rate of 13.3/s. The mechanical properties of LCL were evaluated, with a specific focus on the effect of age. The LMM (Linear Mixed Model) analysis revealed a marginally significant positive slope for Young’s modulus (p = 0.0512) and a significant intercept (p = 0.0016); for Maximum Stress, a negative slope (p = 0.0346) and significant intercept (p < 0.0001); while Maximum Stretch showed a significant negative slope (p = 0.0007) and intercept (p < 0.0001), indicating the muscle reduces compliance and load-bearing capacity with age.