Downie, Calum ORCID: 0000-0002-2614-4809 (2021) Biomechanical, Physiological and Cognitive Factors in Balance Recovery in Older Adults with Knee Osteoarthritis. PhD thesis, Victoria University.

Abstract

Worldwide the population is ageing, and with this there is increased cost of age- related conditions to both the medical system and, importantly, the individual. Falls are a concern amongst this demographic due to potential loss of independence, and even death. Knee osteoarthritis (OA) is a common chronic condition in older adults which increases the risk of falling. Despite 40-50% increased falls risk in people with knee OA, little is known about the mechanism of balance recovery in this group and what comprises a stable response to perturbation when simulating falls. There is also little understanding of the influences of pain and executive function on biomechanical responses to perturbation in this group. Importantly, there has been no investigation, to date, for predicting falls in older adults with knee OA using biomechanical parameters related to balance. The aims of this thesis were to investigate (1) the differences in balance response during induced falls in people with knee OA compared to asymptomatic controls in three trial conditions, (2) the relationship between pain and executive function on balance response, (3) the prediction of falls in older adults with knee OA using the biomechanical parameters associated with balance recovery. Forty-eight older people with knee OA (age average 71.02 ± 6.76 years, BMI average 29.10 ± 4.58 kg/m2, 54% females) and 15 asymptomatic older adults (age average 72.47 ± 4.81 years, BMI average 26.17 ± 3.06 kg/m2, 27% females) were recruited. Participants were placed in an induced lean position and were required to recovery balance when released. Spatio-temporal, upper, and lower limb kinematic and kinetic variables were analysed and compared between the two groups in three different trial types: no additional challenge (neither cognitive nor physical dual-task challenge), cognitive dual-task challenge, and physical dual-task challenge. A convenience sample of 24 OA participants was also selected to complete pain questionnaires and executive function assessments. Finally, participants in the convenience sample completed 12 months prospective falls calendars following baseline data collection. Based on reports of falls in this period, the sample was classified into fallers and non-fallers. The biomechanical measures during balance recovery and other data such as medication usage and patient demographics were used to fit a logistic regression model to predict fallers and non-fallers. When compared to controls, in all conditions, the OA group showed (1) slower and reduced spatio-temporal responses, (2) less ability to absorb impact forces at the knee, and (3) reduced ability to correct motion of the upper body posture. When compared to no additional challenge trials, in the dual-tasking trials there was (4) slower and smaller spatio-temporal responses and (5) greater knee power absorption, and (6) there was significantly reduced knee motion in the OA group. There was some correlation between unstable balance response and pain, in particular reduced hip flexion angular velocity and increased fear of severe pain (moderate positive, p = .02), and increased fear of total pain (moderate positive, p = .03). There was no correlation between unstable response and executive function. Finally, high centre of mass velocity and negative (extension) knee moment during balance recovery tasks were found to be good predictors of falls in older adults with knee OA. The relationship between extension knee moment and prediction of falls was stronger in women. The results from this thesis revealed that, compared to asymptomatic controls, older adults with knee OA took slower and shorter steps, and had a more upright posture following perturbation. Despite the deleterious influence of the spatio-temporal measures arising from the shorter and slower steps, this upright position of the trunk appears to play a part in increasing stability in the OA group via controlling motion of the two thirds of the body’s mass. Increased fear and interference from pain was correlated with lower hip flexion angle, which may also play a part in upright posture. Modelling results suggest a combination of upper body kinematics (velocity of centre of mass) and lower limb kinetics (knee extension moment) could be used to predict future falls in older women with knee OA.

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