The effect of sustained static kneeling on knee joint gait parameters
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Epidemiological studies have identified kneeling as an occupational risk factor for knee joint osteoarthritis (KOA), but direct biomechanical evidence for this relationship is lacking. We hypothesize one mechanism by which prolonged static kneeling may cause KOA is by compromising the integrity of the knee joint thereby increasing knee joint instability, which manifests as altered ambulatory loading profiles. Therefore, the purpose of this exploratory study was to investigate the effect of sustained static kneeling on knee joint gait parameters. Ten healthy male subjects (24.1 years ± 3.5) volunteered for this study. Each subject’s dominant leg was instrumented with markers to track lower limb motion and with surface electromyography electrodes to record quadriceps, hamstrings, and gastrocnemius muscle activity. Subjects performed ten walking trials at a self-selected normal pace over a force plate embedded in the floor. They then performed a kneeling protocol of three bouts of ten minutes of kneeling, each separated by a five minute seated rest period. Subsequently, a set of ten walking trials were performed after a short rest and equipment verification period. The ground reaction force and motion data were used to calculate the peak knee adduction moments, knee flexion moments, and knee flexion angles during the stance phase. The total muscle activity for each muscle during a single gait cycle as well as the co-contraction of the medial thigh muscles and the lateral thigh muscles were calculated from the surface electromyography data. One-sample t-tests were run on the absolute value of the pre- and post-kneeling outcome measures. All outcome measures were different across conditions indicating that the loading patterns were altered, in no specific direction, as a result of the static kneeling protocol. These results offer preliminary evidence to support the epidemiological findings that thirty minutes of daily occupational kneeling is associated with a higher prevalence of KOA. Further investigation is required to explore the importance of post-kneeling recovery, posture-induced blood occlusion, and cartilage stress due to cumulative loading while kneeling, as well as to test the clinical significance of the present findings.