Physiotherapy - Theses
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ItemPost-traumatic knee osteoarthritis after anterior cruciate ligament reconstruction: Psychological, functional and biomechanical factors and the effect of a targeted brace( 2015)Post-traumatic knee osteoarthritis (OA) after anterior cruciate ligament reconstruction (ACLR) is prevalent in younger adults and has the potential to cause substantial knee-related symptoms and limit physical function. Physical and psychological impairments are likely to adversely affect quality of life and work participation. Knowledge of modifiable risk factors associated with knee OA post-ACLR has the greatest capacity to lead to new interventions that could change the natural history of knee OA. What are the modifiable factors associated with knee OA post-ACLR? Section A of this thesis describes the results of two cross-sectional studies which revealed that individuals with knee OA five to 12 years post-ACLR have worse knee confidence and greater kinesiophobia compared with individuals who have no OA five to 12 years post-ACLR. In individuals with knee OA five to 20 years post-ACLR, those with worse knee confidence have worse knee-related symptoms, poorer function, greater kinesiophobia, and poorer perceived self-efficacy and health-related quality of life. Section B of this thesis investigated knee biomechanics during walking in individuals post-ACLR. Pooled data from a systematic review revealed that, compared to healthy controls and uninjured contralateral knees, ACLR knees have abnormal knee biomechanics, particularly in the sagittal plane. Systematic review findings also revealed that the type of graft (hamstring or patellar) and time post-surgery could also influence knee biomechanics. A cross-sectional study also evaluated biomechanics in people with lateral knee OA post-ACLR. Compared to healthy controls, individuals with lateral knee OA five to 20 years post-ACLR had greater knee flexion and lower knee internal rotation angles, as well as greater pelvic anterior tilt, and hip flexion angles. Is there a potential intervention for modifiable risk factors associated with knee OA post-ACLR? A targeted knee brace was investigated for individuals with knee OA post-ACLR. First, a within-subject randomized study investigated the immediate and four-week effects of a targeted knee brace on knee-related symptoms and function in individuals with knee OA post-ACLR. The brace produced improvements in knee-related symptoms immediately and following four weeks of intervention. Second, a within-subject randomized study evaluated the immediate effects of varus bracing on gait characteristics in individuals with lateral knee OA post-ACLR. Results revealed that the unloader brace significantly altered gait characteristics associated with lateral knee OA post-ACLR. Overall, this thesis sheds light on some of the modifiable risk factors associated with knee OA post-ACLR, and investigated one targeted intervention with the potential to improve quality of life of individuals with knee OA post-ACLR. Targeting psychological, functional and biomechanical risk factors in individuals post-ACLR may aid in optimal recovery, and slowing disease progression in individuals with knee OA post-ACLR.
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ItemNeuromuscular control and knee function after anterior cruciate ligament reconstruction( 2014)Knee functional outcomes after anterior cruciate ligament reconstruction (ACLR) are variable, particularly amongst recreational athletes. Functional performance tests and self-reported measures of knee function are used clinically to quantify knee function after ACLR. Although these tests provide some indication of gross-motor function, they do not accurately quantify neuromuscular control. Sub-optimal neuromuscular control may be associated with poor knee function and, in turn, to altered knee joint loading and knee osteoarthritis. Despite years of ACLR research, knowledge of the relationship between neuromuscular control and knee function is limited mostly to bivariate analyses. These analyses do not account for participant characteristics such as age, sex, body mass index, the presence of chondral and meniscal injuries, greater anterior knee joint laxity or the participation limitations experienced by individuals. Knowledge of these associations is necessary to help explain the variability in knee functional outcomes following ACLR. Therefore, the aim of the research reported in this thesis was to investigate the cross-sectional associations between clinical tests of knee joint function and i) sports participation, ii) participant characteristics and iii) neuromuscular control following ACLR. To address this broad aim, four studies were conducted using a cross-sectional, observational study design. Sixty-six participants (23 women, median age 28.4, range 19-39) at an average of 18 months (SD 3 months) following ACLR with an ipsilateral hamstring graft, and 41 matched control participants (16 women, median age 25.8, range 18-39) were recruited. The inter-session reliability and standard error of measurement of variables were determined with 26 control participants (8 women, median age 24.7, range 19-37). In Study 1, the knee function of ACLR and control participants was assessed using a battery of self-reported and functional performance (hop) tests. Compared to control participants, ACLR participants demonstrated significant limitations in self-reported knee function and functional performance and significantly more ACLR participants failed the battery of functional tests. In a multivariate logistic regression model, older age, higher BMI and greater anterior knee joint laxity were significant predictors of failing the battery of knee functional tests. In Study 2, the quadriceps force control and thigh muscle activation strategies of ACLR and control participants were assessed using a novel, sub-maximal intensity, open kinetic chain force-matching task. Participants used quadriceps force to match a moving target torque that was displayed on a screen. ACLR participants demonstrated significantly greater target matching error, indicative of less-accurate quadriceps force production and higher levels of quadriceps activation and hamstring coactivation. In a multivariate linear regression model, less-accurate quadriceps force production was associated with greater vastus lateralis activation, lower lateral hamstring coactivation, female sex, older age at the time of testing, greater anterior knee joint laxity and meniscal surgery at the time of ACLR. Together these variables explained 42% of the variance in quadriceps force control in the ACLR group. In Study 3, the trunk and lower limb biomechanics of ACLR and control participants were compared in the landing phase of a novel forward hopping task which involved a dynamic take-off. Hop distance and take-off velocity were standardised to minimise variability in task performance between individuals. Significantly smaller knee flexion excursion, peak knee extensor moments and peak trunk flexion angles were observed in the ACLR group. In a multivariate linear regression model, greater anterior knee joint laxity, higher vastus medialis activation, lower medial hamstring coactivation and lower quadriceps strength relative to body mass accounted for 54% of the variance in knee flexion excursion in the ACLR group. Study 4 addressed the main aim of the thesis by investigating the multivariate associations between knee joint function, participant characteristics and neuromuscular control. Less-accurate quadriceps force production, greater lateral hamstring coactivation during the force matching task and female sex were significant predictors of failing the functional test battery. In the closed kinetic chain, smaller knee flexion excursion, smaller peak knee extensor moment and greater anterior knee joint laxity were significant predictors of failing the test battery. Prospective studies are now needed to determine whether the biomechanical and neuromuscular variables identified by this research are predictive of long-term knee function and knee osteoarthritis.