Abstract
An exact understanding of the interplay between the articulating tissues of the knee joint in relation to the osteoarthritis (OA)-related degeneration process is of considerable interest. Therefore, the aim of the present study was to characterize the biomechanical properties of mildly and severely degenerated human knee joints, including their menisci and tibial and femoral articular cartilage (AC) surfaces. A spatial biomechanical mapping of the articulating knee joint surfaces of 12 mildly and 12 severely degenerated human cadaveric knee joints was assessed using a multiaxial mechanical testing machine. To do so, indentation stress relaxation tests were combined with thickness and water content measurements at the lateral and medial menisci and the AC of the tibial plateau and femoral condyles to calculate the instantaneous modulus (IM), relaxation modulus, relaxation percentage, maximum applied force during the indentation, and the water content. With progressing joint degeneration, we found an increase in the lateral and the medial meniscal instantaneous moduli (p < 0.02), relaxation moduli (p < 0.01), and maximum applied forces (p < 0.01), while for the underlying tibial AC, the IM (p = 0.01) and maximum applied force (p < 0.01) decreased only at the medial compartment. Degeneration had no influence on the relaxation percentage of the soft tissues. While the water content of the menisci did not change with progressing degeneration, the severely degenerated tibial AC contained more water (p < 0.04) compared to the mildly degenerated tibial cartilage. The results of this study indicate that degeneration-related (bio-)mechanical changes seem likely to be first detectable in the menisci before the articular knee joint cartilage is affected. Should these findings be further reinforced by structural and imaging analyses, the treatment and diagnostic paradigms of OA might be modified, focusing on the early detection of meniscal degeneration and its respective treatment, with the final aim to delay osteoarthritis onset.
Highlights
Knee joint osteoarthritis (OA) is a prevalent and disabling disease that globally incurs increasing socioeconomic costs (Neogi, 2013)
Following separation of the femur from the tibial plateau with the menisci remaining attached, the distal part of the femur was cut through a horizontal plane with a band saw to permit mounting on a sample holder (Figure 1A), which was installed in a testing chamber filled with phosphate-buffered saline (PBS)
Regarding the water content of the tibial articular cartilage (AC), we found an increase of approximately 3% with progressing degeneration
Summary
Knee joint osteoarthritis (OA) is a prevalent and disabling disease that globally incurs increasing socioeconomic costs (Neogi, 2013). On the other hand, degenerated knee joints indicate degenerative changes of the menisci, including tears, macerations, and tissue loss (Bhattacharyya et al, 2003; Hunter et al, 2006; Englund et al, 2009), thereby leading to controversy in the treatment of knee joint OA, as summed up by Englund et al (2009): “A meniscal tear can lead to knee OA, but knee OA can lead to a meniscal tear.” Both articular cartilage (AC) (Silvast et al, 2009; Marchiori et al, 2019; Ebrahimi et al, 2020) and menisci (Fithian et al, 1990; Fox et al, 2012; Son et al, 2013; Danso et al, 2017; Travascio et al, 2020a,b; Warnecke et al, 2020; Morejon et al, 2021) are highly anisotropic and inhomogeneous tissues that exhibit strong structure–function relationships that change during the course of OA degeneration. It can be stated that these converse tissue degeneration effects might result in an excessive abrasion of the cartilage tissue accompanied by meniscal tissue calcification, which may accelerate knee joint OA progression
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