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 and biomechanical factors in people following partial meniscectomy( 2014)Arthroscopic partial meniscectomy (APM) is a common surgical procedure for meniscal tears and knee osteoarthritis (OA) is often reported in people who have undergone an APM. Knee OA is a major public health problem worldwide causing pain and disability, for which there is currently no cure. Cross-sectional data suggest that people following APM have a higher knee adduction moment (KAM, an indicator of medial to lateral knee load distribution) during gait, as well as reduced knee extensor muscle strength compared to healthy controls. These factors are potential contributors to knee OA and are potentially modifiable with appropriately targeted treatments. However, prospective studies are needed to identify if these modifiable risk factors contribute to the development of structural changes to knee joint cartilage in this group. Moreover, interventions that target identified modifiable risk factors for knee OA in people following APM are urgently required to combat the individual and societal burden of the disease. Part I of this thesis describes analyses from a prospective longitudinal study that included 82 people assessed 3 months following medial APM and re-assessed 2 years later (n=66). A comparison control group of 38 healthy participants was also assessed at baseline and 2 years (n=23). Exploratory analyses revealed that the APM cohort had a higher KAM during gait and weaker knee extensor and flexor muscle strength compared to controls at 3 months following surgery. However, knee muscle strength improved in the APM cohort over time, such that no differences in strength were found 2 years later compared to controls. Peak KAM increased in the APM leg over 2 years, although this change in KAM over time was not significantly different to that seen in controls. An investigation into the mechanisms that might explain the increase in peak KAM following APM was performed. Results indicated that an increased varus position of the tibia during gait partially explained the 2-year increase in peak KAM in people following APM. Further analyses found no evidence to suggest that knee muscle weakness at 3 months predicted 2-year change in KAM. Part I also evaluated whether alterations in the KAM and knee extensor strength were associated with measures of knee joint structural change (cartilage defects and cartilage volume). These analyses demonstrated that in people 3 months following APM, a higher peak KAM during fast pace walking, but not knee muscle strength, was associated with medial tibiofemoral cartilage defect onset or deterioriation over the subsequent 2 years. Part II of this thesis describes a single-blind randomised controlled trial conducted to evaluate the effects of a specific neuromuscular exercise program (‘ALIGN’) on the peak KAM during gait and a one-leg sit-to-stand task in 62 people who had undergone APM 3-12 months earlier. Secondary outcome measures included peak KAM during fast pace gait, one-leg hop for distance, peak KAM impulse during one-leg sit-to-stand task, knee and hip muscle strength, objective measures of physical function and self-reported measures of physical function and symptoms. Findings showed that the neuromuscular exercise program did not significantly change the peak KAM during gait or a one-leg sit-to-stand task. No between-group differences were found for any of the secondary outcomes. Overall, this thesis provides some evidence to suggest that a higher peak KAM during gait may be related to knee cartilage degradation over time following APM. Interventions that aim to improve varus malalignment of the tibia could potentially delay or prevent structural changes to knee joint cartilage following APM. However, the neuromuscular exercises included in this research did not reduce the KAM during gait or a one-leg sit-to-stand task. Nevertheless, we did not quantify structural change in this study; we therefore cannot conclude that neuromuscular exercise fails to delay or prevent osteoarthritic structural change in APM patients.
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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.
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ItemKnee motion and foot speed at and around initial contact in human gait( 2014)Biomechanical analyses have provided detailed information about joint kinematics and kinetics of the gait cycle. Interpretation of this data has largely overlooked (Winter, 1983a), or even misrepresented (Cerny, 1984; Perry, 1992), knee kinematics around initial contact (IC). It has been suggested that heel speed (HS) approaches zero magnitude as a way of preparing the foot for landing at IC and that knee kinematics influence this event (Winter, 1992b). A number of factors, including the re-introduction of ground reaction forces to the leading limb, make IC a complex event within the gait cycle. The aim of this study was to clarify knee joint kinematics at and around IC in human gait. Three hypotheses were tested. Firstly, that knee flexion (KF) precedes IC. Secondly, that the quantum of knee flexion and the percentage of stride spent flexing the knee prior to initial contact are dependent on gait speed. And thirdly, that HS is reduced to near zero magnitude in preparation for contact with the ground at the start of stance phase. Sixteen healthy, young adults participated in this study. A Vicon 3D Infra-red motion analysis system (Oxford Metrics Ltd., Oxford, England) sampling at 120 Hz and AMTI Force Plates (Advanced Mechanical Technology, Inc., Watertown, USA) sampling at 1080 Hz were used to record kinematic and kinetic data from walking trials at each of three self-selected speeds: slow; preferred and fast. Data were extracted representing the timing of the onset of KF prior to IC, the amount of KF occurring between maximum knee extension prior to IC and IC as well as HS at IC. The data were assessed for normality using the Kolmogorov-Smirnov test of normality and through skewness and kurtosis. Friedman’s χ2r statistic and RM MANOVAs were used to investigate differences across gait speed. Post hoc testing was performed with the Wilcoxon test and contrasts testing. KF data were found to be non-normal. At preferred speed 2.6% of stride was taken up flexing the swinging knee 1.4° prior to IC. This rose to 3.5% of stride and 2.3° of flexion prior to IC at fast speed and fell to 2.2% of stride and 0.8° of flexion prior to IC at slow speed. The quantum of KF prior to IC also increased with gait speed. All HS data were normal. Mean HS at IC was 559.7mm•s-1 at preferred speed. Mean HS at IC rose to 841.3 mm•s-1 at fast speed and fell to 391.2 mm•s-1 at slow speed. KF and HS were found to be significantly different across speeds (p < 0.001). Results support the hypothesis that KF occurs prior to IC in human gait. The amount and duration of this KF were dependent upon walking speed. These findings suggest that in human gait a motor control strategy is implemented where the knee flexes in anticipation of initial contact. This repudiates the common perception in the gait literature that the knee is extended, or stable in extension at IC (eg Gage, 1990; Cerny, 1984). Whilst HS does slow late in swing the results of this study do not support the proposition that a function of knee motion prior to IC is to reduce HS to near zero magnitude. The outcomes of this study provide clinicians with crucial information to guide decision making with respect to gait analysis and training.
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ItemGait modification strategies for people with medial knee osteoarthritis( 2012)Knee osteoarthritis, most commonly occurring in the medial compartment, is a leading cause of pain and disability among the elderly. During gait, greater compressive load in the medial compartment is a major risk factor for osteoarthritis. As there is currently no cure, interventions which can reduce compressive loads are needed, because of their potential to slow disease progression. Evaluated during gait, the knee adduction moment is a commonly used surrogate measure of medial knee load and a marker for medial knee osteoarthritis progression. One of the conservative biomechanical approaches which may reduce the knee adduction moment is gait modification, or gait retraining. However, little is known about the strategies and their effects on medial knee load. Firstly, a systematic literature review was conducted to identify gait modifications. Of the 14 gait modifications identified in 24 studies, four strategies demonstrated greatest ability to reduce the knee adduction moment. Several limitations of previous studies were identified, such as poor reporting of methods, inclusion of participants without osteoarthritis, no evaluation of symptoms and limited information regarding the amount of modification required. Because of demonstrated ability to reduce a parameter of the knee adduction moment in cohorts, the following modifications were investigated in separate studies involving participants with symptomatic medial knee osteoarthritis: use of a cane on the contralateral side, increased lateral trunk lean and altered foot progression angle. The effects of contralateral cane use on knee load and pain were investigated in 23 individuals. Participants placed pre-determined magnitudes of support through the cane. Findings showed reductions in all knee load parameters, with a dose-response relationship. Likely due to biomechanical advantages, the technique of cane use influenced the load-reducing efficacy, such as cane positioning and timing of support. Whilst there were no changes in pain with cane use, individuals with greater severity of pain and varus malalignment reduced load more effectively. The effects of ipsilateral trunk lean gait on the knee adduction moment and pain were investigated in 22 individuals. Participants walked with varying magnitudes of trunk lean. Results demonstrated dose-response reductions in all knee load parameters, whilst pain remained unchanged. Timing of the gait modification mediated the efficacy of load reduction. Lastly, effects of altered foot progression angle on pain, the knee adduction and knee flexion moments were investigated in 22 individuals. Participants walked with varying degrees of toe-in and toe-out gait. Whilst pain remained unchanged, toe-in gait reduced the knee adduction moment during early stance but increased the knee flexion moment, knee adduction impulse and late stance adduction moment. Toe-out gait demonstrated opposite effects to toe-in gait. Furthermore, pain and malalignment demonstrated significant mediating effects for some outcomes. This thesis reports new and clinically relevant information on gait modifications for people with medial knee osteoarthritis. It was discovered that participant characteristics, the magnitude of modification and technique of performance altered the efficacy of load reduction achieved by gait modification strategies. Although future longitudinal evaluations are required, gait modifications investigated in this thesis may have potential to slow osteoarthritis progression via load reduction.