Biomechanical Analysis of the Knee Joint Load During a Unilateral Sit-to-Stand Movement

Background and Objectives: Sit-to-Stand (STS) movements are fundamental activities of daily living. As STS movements can be physically demanding especially for the elderly, bi- and unilateral STS movements are frequently used in motor tests to measure lower limb strength. In contrast to bilateral STS movements, the knee joint loads occurring during unilateral STS movements as well as the influences of chair height or lower limb dominance are still unknown. Methods: In a randomized study approach knee joint loads during unilateral STS movements from three different chair heights have been analyzed using biomechanical motion analysis in a population of 19 healthy middle-aged adults. Additionally, the influence of lower limb dominance and the level of perceived exertion have been investigated. Results: Lower limb dominance had no effect on knee joint load. In contrast, chair height significantly affected the peak shear forces in anterior (high: 3.94 ± 0.63 N/kg; low: 4.09 ± 0.61 N/kg) and lateral (high: 1.52 ± 0.79 N/kg; low: 1.78 ± 0.88 N/kg) direction as well as the peak knee adduction moment (high: 0.56 ± 0.29 Nm/kg; low: 0.65 ± 0.32 Nm/kg). Additionally, chair height but not limb dominance significantly affected the level of perceived exertion (high: 11.1 ± 2.8; low: 12.5 ± 3.5). Conclusion: The detected knee joint loads occurring during a unilateral STS movements are similar to those of other activities of daily living like e.g. stair ascent and thus, unilateral STS movements are applicable for usage in motor tests for middle-aged subjects. While lower limb dominance has no impact on the knee joint load, lower chair heights increase the load on the knee joint. Therefore, chair height should be considered when using unilateral STS movements in motor tests.

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Energy absorption at lower limb joints in different foot contact strategies while descending stairs

Technology and Health Care ◽

10.3233/thc-218041 ◽

2021 ◽

Vol 29 ◽

pp. 433-440

Author(s):

Hyeong-Min Jeon ◽

Ki-Kwang Lee ◽

Jun-Young Lee ◽

Ju-Hwan Shin ◽

Gwang-Moon Eom

Keyword(s):

Knee Joint ◽

Potential Energy ◽

Energy Absorption ◽

Lower Limb ◽

Mechanical Energy ◽

Connective Tissues ◽

Stair Descent ◽

Young Subjects ◽

Power And Energy ◽

Joint Loads

BACKGROUND: Joint loads in different walking strategies during stair descent have been investigated in terms of the joint moment in association with the risk of osteoarthritis. However, the absorption mechanisms of the potential energy loss are not known. OBJECTIVE: This study aims to compare the mechanical energy absorptions in lower limb joints in different initial foot contact strategies. METHODS: Nineteen young subjects walked down on instrumented stairs with two different strategies, i.e., forefoot and rearfoot strike. Power and energy at lower limb joints during stance phase were compared between strategies. RESULTS: Lower limb joints absorbed 73 ± 11% of the potential energy released by descending stairs and there was no difference between strategies. Rearfoot strategy absorbed less energy than forefoot strategy at the ankle joint in the 1st phase, which was compensated mainly by more energy absorption at the knee in the 2nd phase and less energy generation at the hip joints in the 3rd phase. CONCLUSION: The results suggest that a leg absorbs most of the potential energy while descending stairs irrespective of the walking strategies and that any reduction of energy absorption at one joint is compensated by other joints. Greater energy absorption at the knee joint compared to the other joints suggests high burden of knee joint muscles and connective tissues during stair-descent, which is even more significant for the rearfoot strike strategy.

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