The Effect of Knee Postures and Cushions in the Load Transmission of Impact Loading - An in Vitro Biomechanical Porcine Model

Abstract

Degenerative osteoarthritis is the consequence of impact force applied to articular cartilage that results in surface fissuring. Soft cushions and flexed posture are two important factors to reduce the impact force; however, no quantitative information of how soft should the cushion be to prevent the injury and the mechanism of force attenuation of knee joint at neutral and flexed posture was not well documented yet. The objective of current study is hence to find the quantitative shock attenuation of knee joint using different stiffness of cushions when the knee is at neutral posture and flexed posture. A “drop-tower type” impact apparatus was used for testing. Nineteen fresh porcine knee joints were divided into two posture groups, i.e. neutral and flexed posture. All specimens were tested using stiff, medium, and soft cushions. The axial reaction force, anteroposterior shear force, and flexion bending moment were recorded for analysis. We found the flexed posture decreased the axial reaction force and anterior shear force but increased the flexion bending moment. The effect of stiffness of cushions on the mechanical response of knee joint during impact loading was significant for neutral posture but not for flexed posture.

The menisci are not shock absorbers: A biomechanical and comparative perspective

“…Though slight, even this amount of knee flexion can dramatically reduce the magnitude of impact transient force at the knee. Indeed, in the knee loading experiments of Wang and Lee (2004), which used a similar methodology to Hoshino and Wallace (1987), found that even slight flexion of 10 was associated with a nearly 50% reduction in axial force transmission. Energy absorption occurs through negative muscle work within the first 25% of the stride via eccentric contraction of the quadriceps femoris in both walking and running (Orendurff et al, 2018;Winter, 2009).…”

“…First, this study uses knees that are fixed in full extension. More recent studies using the same experimental paradigm have shown that even slight knee flexion (10°), like that which occurs at, and immediately after, heel strike (Fukuchi, Fukuchi, & Duarte, 2017, 2018; Kadaba, Ramakrishnan, & Wootten, 1990) reduces axial force magnitude by about half (Wang & Lee, 2004). Furthermore, an additional study using a similar experimental design but with accelerometers to better measure impact propagation and attenuation along the tibia and femur (Chu et al, 1986) demonstrated a much smaller effect.…”