Background Characterizing knee contact loads across diverse movements and in the presence of cognitive challenges is necessary to understand occupational factors associated with knee osteoarthritis risk in manual laborers (e.g., agricultural workers).

Research Questions What are the tibiofemoral contact forces during walking, kneel-to-stand, and jump landing and how do cognitive challenges affect these contact forces?

Methods Twenty-four healthy manual laborers and recreational athletes completed walking (WALK), standing from a kneeling position (KNEEL), and jump landings (JUMP), each with a cognitive challenge (COG) and without (BASE). Neuromusculoskeletal modelling was used to estimate tibiofemoral contact forces. Peak tibiofemoral contact forces (medial, lateral, and total) during the stance phase were primary outcomes. Correlations between peak contact forces across tasks and comparisons of contact force time series were also evaluated.

Results There were no significant Task*Condition interactions or main effects of Condition; however, there was a main effect of Task for peak medial, lateral, and total tibiofemoral contact forces (P<0.001). Tibiofemoral contact forces during WALK were poorly related to corresponding estimates during KNEEL or JUMP (r=0.13±0.08), but KNEEL and JUMP were significantly related (r=0.64±0.16). COG resulted in increased medial contact forces during the 28-66% of stance phase for KNEEL.

Significance The differences in loading magnitude alongside a lack of rank-order consistency between contact loads during walking with those during more dynamic tasks motivates the need to sample a representative range of motor tasks and situational demands for the population of interest to reflect real-world contact loads and study their relation to knee osteoarthritis.

A reactive challenge increased medial knee loading when rising from kneeling

Cognitive challenges had variable and often negligible effects on contact forces

Rising from kneeling had increased peak knee contact forces than walking

Peak tibiofemoral contact forces for rising from kneeling were at deep knee flexion

Knee contact forces during walking did not relate to those during other tasks

The authors have declared no competing interest.

This study was funded by P20GM103474 – MT INBRE II: A Multidisciplinary Research Network; Administrative Core; Montana INBRE II: A Multidisciplinary Research Network; P20GM104417 – Center for Health Equity in Rural Montana; and the Montana State University Office of the Vice President for Research and Economic Development

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

IRB of Montana State University gave ethical approval for this work under protocol number SM110421

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Location Research was Conducted: Neuromuscular Biomechanics Laboratory, Montana State University, Bozeman, Montana, USA

All data produced in the present study are available upon reasonable request to the authors