The shock attenuation properties of straight standing knee joints using different shock absorbers and energy inputs

Exposure of human lower extremities to mechanical loading will lead to different biological responses, e.g., degenerative and post‐traumatic osteoarthritis. Relations among injuries and impact energy have been well studied. However, how the external force is attenuated by the internal joint is not known yet. The objective of the current study is to find the shock attenuation properties of knee joint using different shock absorbers. A “drop‐tower type” impact apparatus was used for testing. Ten fresh porcine knee joints were aligned at full extension for testing. All specimens were tested at 30 and 40 mm levels of height, 12 and 16 kg levels of weight, and with shock absorbers of 20 (stiff), 40 (medium), and 60 (soft) mini‐seconds levels of contact time. The impact forces, flexion moment and all directions of acceleration were found to decrease with a softer shock absorber. A medium shock absorber produces 33% less axial force, 68% less shear force, 53% less bending moment and more than 70% less accelerations at femur and tibia compared to the stiff shock absorber. The results of the current research can be used for reference in designing sports footwear.