Abstract
While it is generally accepted that traumatic meniscus pathologies lead to degenerative articular cartilage changes in the mid-to long-term and consecutively to post-traumatic osteoarthritis (PTOA), very little is known about how such injuries initiate tribological changes within the knee and their possible impact on PTOA acceleration. Therefore, the aim of this study was to investigate the influence of three different medial meniscus states (intact, posterior root tear, total meniscectomy) on the initial whole knee joint friction. Six ovine knee joints were tested in a passive pendulum friction testing device under an axial load of 250 N and an initial deflection of 12°, representing swing phase conditions, and under an axial load of 1000 N and an initial deflection of 5°, simulating stance phase conditions. To additionally consider the influence of the time-dependent viscoelastic nature of the knee joint soft tissues on whole joint friction, the tests were performed twice, directly following load application and after 20 min creep loading of either 250 N or 1000 N axial load. On the basis of a three-dimensional joint kinematic analysis, the energy loss during the passive joint motion was analyzed, which allowed considerations on frictional and damping processes within the joint. The so-called “whole knee joint” friction was evaluated using the boundary friction model from Stanton and a viscous friction model from Crisco et al., both analyzing the passive joint flexion-extension motion in the sagittal plane. Significantly lower friction coefficients were observed in the simulated swing phase after meniscectomy (p < 0.05) compared to the intact state. No initial whole joint friction differences between the three meniscus states (p > 0.05) were found under stance phase conditions. Soft tissue creeping significantly increased all the determined friction coefficients (p < 0.05) after resting under load for 20 min. The exponential decay function of the viscous friction model provided a better fit (R 2∼0.99) to the decaying flexion-extension data than the linear decay function of the boundary friction model (R 2∼0.60). In conclusion, this tribological in vitro study on ovine knee joints indicated that neither a simulated posterior medial meniscus root tear nor the removal of the medial meniscus resulted in an initially increased whole joint friction.
Highlights
The menisci are two semi-lunar shaped fibrocartilages that are located between the tibia and femur inside the knee joint and play an essential role in sustaining knee joint health
The aim of this study was to investigate the influence of a posterior medial meniscus root (PMMR) tear and a consecutive MM on the energy loss during passive motion of ovine knee joints using a passive pendulum friction test setup
The analysis of the energy loss over time enables considerations on friction and damping processes in the joint, which both contribute to a decay of the pendulum motion over time
Summary
The menisci are two semi-lunar shaped fibrocartilages that are located between the tibia and femur inside the knee joint and play an essential role in sustaining knee joint health. Their wedgeshaped cross-section is of decisive importance for load transmission in the joint, because up to 50% of the compressive loads across the knee are transmitted via the lateral and medial menisci (Jones et al, 2006). While the fluid phase mainly consists of water, the solid phase is comprised of an extracellular matrix with collagen and proteoglycans as major components (Mow and Huiskes, 2005). Joint motion is lubricated by the synovial fluid, which consists of hyaluronic acid, water, proteins, lipids and glucose (Bortel et al, 2015; Kosinska et al, 2015; Lin and Klein, 2021)
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