Methods

Menisci of 24 TKR-patients (≈67.1 yrs.) were harvested and the degeneration of each region (pars anterior PA, pars intermedia PI, pars posterior PP) classified according to Pauli et al. For biomechanical characterisation, confined compression tests (20% strain; velocity: 3%h₀/min, relaxation time: 1h) to determine equilibrium modulus (H_A) and hydraulic permeability (k) and tensile tests (velocity: 5%l₀/min) to determine the tensile modulus were performed. Therefore, cylindrical (Ø= 4.6mm, initial height h₀≈ 2.3mm) and dumbbell-shaped (3.5mm × 1.4mm × 3.5mm) samples were punched out of each region and flattened to achieve parallel surfaces. Additionally, collagen and proteoglycan (PG) content were analysed by calculating the area-under-curve of their specific wavelength ranges (1293–1356cm⁻¹ and 980–1120cm⁻¹, respectively) using infrared (IR) spectroscopy. To identify differences regarding the meniscus regions or its degeneration, a statistically mixed model was used.