Physiotherapy - Theses
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ItemInfluence of female pubertal development and athletic footwear on lower limb biomechanics: implications for non-contact ACL injury and patellofemoral pain( 2017)Adolescent girls are susceptible to knee injuries such as non-contact anterior cruciate ligament (ACL) rupture and patellofemoral pain (PFP). Adolescence is synonymous with pubertal development which drives substantial growth and maturation of the musculoskeletal system, and is thought to contribute to poor knee biomechanics associated with both of these injuries. Specifically, higher tri-planar knee moments during puberty (external peak knee abduction moment (KAbM), flexion moment (KFM) and internal rotation moment (KIRM)) are thought to contribute to a higher incidence of these injuries; however, there are still gaps in our understanding of female pubertal biomechanics. For instance, variations in dynamic tasks (i.e., bilateral vs single limb), unreliable pubertal classification methods, small sample sizes, conflicting findings and data normalisation methods (i.e., mixed between body mass or body mass by height) highlight the need for additional, better designed pubertal studies. The role of athletic footwear is also an important consideration, given it may alter tri-planar knee moments relevant to both non-contact ACL rupture or PFP. Specifically, high-support footwear is thought to control excessive foot pronation, which may transfer up the kinetic chain and confer protection at the proximal knee joint by modifying tri-planar knee moments during dynamic tasks. By contrast, low-support shoes do not possess the same stability features, potentially allowing for greater foot pronation that may have a clinically meaningful effect on tri-planar knee moments compared to high-support shoes. Surprisingly, no studies have explored the effects of these shoes during female pubertal development, which is concerning as many adolescent girls are likely wearing these types of shoes during the various sports in which the aforementioned knee injuries occur. To address the current limitations in pubertal and footwear biomechanical research, four cross-sectional studies are reported in this thesis. Ninety-three girls aged between 7-25 years old were categorised into three key stages of puberty: pre-pubertal (n = 31, mean age = 9.4 ± 1.2), early/mid-pubertal (n = 31, mean age = 11.1 ± 1.4) and late/post-pubertal (n = 31, mean age = 19.8 ± 4.0). Tri-planar knee moments normalised to body mass (Nm/kg) and body mass by height (Nm/kg/m) were analysed across landing and running-related tasks in each pubertal group. These were initially observed barefoot, and then subsequently, the effect of high- and low-support footwear was explored across both tasks. The primary aim of Study 1 was to determine whether peak tri-planar knee moments differed between three stages of female pubertal development during a barefoot single limb drop lateral jumping (DLJ) task. The secondary aim was to explore the hip adduction moment (HAM) at time of peak KAbM and the hip flexion moment (HFM) at time of peak KFM between pubertal groups. In the frontal plane, a higher peak KAbM was found for the late/post- compared to the pre-pubertal group when normalised to body mass (95%CI=-0.02 to -0.17 Nm/kg, p=0.015, d=0.61), but not body mass by height (p=0.88). At the hip, neither body mass or body mass by height normalised data revealed between-group differences for HAM at time of peak KAbM (p>0.05). In the sagittal plane, a higher peak body mass-normalised KFM was found for the late/post- (95%CI=0.19 to 0.68 Nm/kg, p=0.001, d=1.12) and the early/mid-pubertal groups compared to the pre-pubertal group (95%CI=0.05 to 0.52 Nm/kg, p=0.017, d=0.59). No significant between-group differences were found for body mass by height-normalised peak KFM (p=0.30) or the HFM at time of peak KFM (p>0.05). Finally, in the transverse plane, a higher peak KIRM in the late/post- compared to both the early/mid- (95% CI = -0.09, -0.01 Nm/kg, p=0.028, d=0.62) and pre-pubertal groups (95% CI= -0.12, -0.03 Nm/kg, p=0.001, d=0.82) was found for body mass, but not body mass by height normalised data. The primary aim of Study 2 was to determine whether peak tri-planar knee moments differed across footwear conditions (i.e., barefoot, high-support and low-support shoes) during the single-limb DLJ amongst late/post-pubertal girls. Based on the findings in Study 1, the late/post-pubertal group was selected as they displayed higher mass normalised tri-planar knee moments compared to early/mid- and pre-pubertal counterparts and may be at higher risk of ACL injury. Results revealed no significant differences for peak KAbM or KIRM regardless of statistical adjustment for FPI (p>0.05). By contrast, peak KFM was higher in the high-support (95% CI= 0.36, 0.53 Nm/kg, p<0.001, d= 1.11) and low-support shoes (95% CI= 0.25, 0.48 Nm/kg, p<0.001, d= 0.85) compared to barefoot; however, no significant differences were observed between shoe conditions. Together, Study 1 and 2 provide novel insights into the effects of female puberty and footwear on the biomechanics of single-limb landing, revealing that increased pubertal-related height (i.e., stature), rather than body mass, is the main contributor to augmented tri-planar knee moments in the latter stages of female pubertal development, which athletic footwear did not ameliorate. The primary aim of Study 3 was to examine tri-planar knee moments (normalised to body mass and body mass by height) across the three pubertal stages while running barefoot. Higher peak body mass-normalised KFM was apparent in the late/post-pubertal (95% CI= 0.18 to 0.63 Nm/kg, p=0.001, d= 1.01) and early/mid-pubertal (95% CI= 0.02, 0.47 Nm/kg, p=0.034, d=0.52) girls compared to the pre-pubertal girls; however, no significant differences were found when KFM was normalised to body mass by height (p>0.05). Furthermore, no significant differences were found for body mass or body mass by height normalised peak KAbM or KIRM (p>0.05). At the hip, a lower body mass normalised HAM at time of peak KFM (i.e., greater hip abduction moments) was found in the late/post- (95% CI= -0.51, -0.11 Nm/kg, p=0.003, d= 0.86) and early/mid-pubertal (95% CI= -0.42, -0.01 Nm/kg, p=0.039, d= 0.53) girls compared to their pre-pubertal counterparts. Likewise, in the sagittal plane a decrease in body mass normalised HFM at time of peak KFM was evident with the late/post-pubertal girls displaying lower HFM (95% CI= 0.65, 0.28 Nm/kg, p<0.001, d=1.27) compared to their early/mid- and pre-pubertal counterparts (95% CI= 0.36, 0.73 Nm/kg, p<0.001, d=1.42). Study 4 determined whether footwear conditions (i.e., barefoot, high-support, low-support) effect running-related peak KFM amongst a pooled sample of early/mid- and late/post-pubertal girls. Based on the findings in Study 3, girls in the early/mid- and late/post-pubertal groups were pooled as no differences in body mass normalised tri-planar knee moments were observed; however, they both displayed higher peak KFM compared to pre-pubertal girls. The secondary aim explored predictors associated with a change in the peak KFM wearing shoes compared to barefoot (i.e., knee-ground reaction force (GRF) lever arm, sagittal plane resultant GRF magnitude and sagittal plane lower limb kinematics) to help elucidate the underlying biomechanical mechanism. A main effect (p<0.001) for peak KFM was found, revealing both high- (95% CI= 0.36, 0.49 Nm/kg, p<0.001, d=1.07) and low-support (95% CI= 0.31, 0.45 Nm/kg, p<0.001, d=0.97) footwear increased peak KFM compared to barefoot, no differences were found between shoes (p>0.05). The regression models identified that only a change in the knee-GRF lever arm in shoes compared to barefoot was associated with a change in peak KFM (F(1, 109)= 93.56, p<0.001), but not the sagittal plane GRF magnitude or any lower limb kinematics (p>0.05). Combined, Study 3 and 4 provide evidence for a developmental increase in sagittal plane but not frontal or transverse plane knee moments that are likely attributed to differences in adolescent height while running. More importantly, wearing shoes increased peak KFM even further regardless of whether they possessed supportive characteristics, and this was partly driven by an increase in the knee-GRF lever arm. Given the repetitive and chronic loading pattern associated with the development of adolescent PFP, both puberty and athletic footwear may influence the manifestation of this condition. Further studies are required to prospectively determine whether higher body mass landing-related tri-planar knee moments and running-related peak KFM in the later stages of puberty are indeed linked to ACL rupture or PFP, respectively. Moreover, pubertal footwear studies may consider modifying footwear features to determine if these higher knee moments can be attenuated.
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ItemNeuromuscular and biomechanical adaptations associated with chronic low back pain( 2016)Neuromuscular adaptations are a hallmark presentation of chronic low back pain (CLBP). People with CLBP have demonstrated trunk muscle co-contraction, trunk muscle weakness and decreased lumbar range of motion (ROM). The relationship between traditional neuromuscular assessments (e.g., lumbar ROM or trunk muscle strength) and self-reported disability is low. Arguably, the measurement of trunk ROM and trunk muscle strength are non-specific and cannot adequately explain the variances in disability in CLBP. Perhaps novel assessments assessing different domains of neuromuscular adaptations can better explain variances in self-reported disability in people with CLBP. Novel assessment of knee muscle force control demonstrated an impairment in the quadriceps ability to produce an accurate force in anterior cruciate ligament reconstructed (ACLR) population compared to healthy cohort. The assessment of muscle force control has not been performed in the CLBP cohort. Similarly, the assessment of inter-joint coordination using relative phase angle analysis was originally developed to identify safe lifting technique in manual workers but has not been performed in CLBP cohort. Therefore the aims of this thesis were i) to compare CLBP and healthy participants on novel trunk muscle force control assessment, ii) to compare CLBP and healthy participants on the assessment of lifting inter-joint coordination and iii) to investigate the relationship between self-reported disability and the aforementioned novel neuromuscular assessments in people with CLBP. To address these aims, four cross-sectional studies were conducted. Forty three participants with CLBP (mean Oswestry Disability Index (ODI) = 22.1 ± 13.2, mean pain Numerical Rating Scale (NRS) = 3.6 ± 1.9) and 29 matched healthy control participants were recruited. Inter-session reliability were assessed on 17 CLBP participants and 16 healthy participants. Study 1 compared and described the participant characteristics with respect to pain and self-reported disability quantified using NRS and ODI respectively. The findings demonstrated that people with CLBP reported significantly higher level of pain and disability than healthy participants. Incidentally, CLBP participants were nine years older than healthy people. Study 2 compared lumbar extensor maximal voluntary isometric contraction (MVIC) and lumbar extensor muscle force control in people with CLBP and healthy people using a novel force matching protocol adapted from studies in the quadriceps. The assessment protocol utilised a force target varied between 20%-50% MVIC (i.e., increasing and decreasing force output). No significant differences in lumbar extensor MVIC were evident between the groups. CLBP group demonstrated increased force matching error compared to healthy people, suggestive of impairment in lumbar extensor muscle force control. People with CLBP demonstrated more error when increasing force production compared to when decreasing force production. Study 3 compared kinematic and vertical ground reaction force assessment during a lifting task in people with and without CLBP. Participants with CLBP were characterised based on their disability phenotype (i.e., higher and lower disability). In addition to the measurement of trunk and lower limb ROM and angular velocity, trunk and lower limb joint coordination was assessed using relative phase angle analysis. There was no significant difference in trunk and lower limb ROM and angular velocity between all groups. Both groups demonstrated similar lifting trunk and lower limb joint coordination pattern and vertical ground reaction force pattern. However, people with CLBP took longer to lift a light load compared to healthy controls. Study 4 investigated the relationship between the assessments outlined in Studies 2 and 3 and ODI. There was no significant correlation between lumbar extensor MVIC, trunk and lower limb ROM and angular velocity during lifting and ODI. One unit increase in error when decreasing force production was associated with 47% increase in ODI. Similarly, one second increase in coordinated movement duration between the thorax and lumbar spine was associated with 47% increase in ODI. The amount of error when decreasing force output and duration of coordinated movement between the thorax and lumbar spine explained 27% of ODI variance. The findings of this thesis suggest that the assessment of lumbar extensor muscle force control and inter-joint coordination during lifting explain a significant portion of self-reported disability; thus, these measures are valid for CLBP patients. Future research is required to investigate whether improvement in the novel neuromuscular variables are associated with a decrease in self-reported disability.
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ItemBiomechanical and neuromuscular impairments in individuals with gluteal tendinopathy( 2016)Gluteal Tendinopathy (GT) is a typically chronic, recalcitrant cause of lateral hip pain most commonly seen in women aged 40 to 70 years. The condition involves pathology of the gluteus minimus and/or gluteus medius tendons at or above their insertion into the greater trochanter of the femur. Clinically, symptomatic GT presents as pain around the greater trochanter, aggravated during single leg loading in walking and stair climbing, and can have a major impact on function. Based on clinical observation it has been hypothesized that individuals with GT exhibit altered biomechanics and neuromuscular control during single leg loading tasks; specifically increased pelvic drop and hip adduction, which might modify gluteal tendon loading at the greater trochanter contributing to the development and/or perpetuation of the condition. However, despite clinical assessment and treatment for GT often being based on these presumed impairments, little is known about the biomechanical or neuromuscular impairments in individuals with GT. Given evidence of muscle weakness in other lower limb tendinopathies, and that strengthening exercise appears to be an effective management strategy for tendinopathy, Study 1 aimed to establish whether individuals with GT exhibit hip abductor muscle strength deficits when compared to pain-free controls. Interestingly, not only did Study 1 identify hip abductor weakness of the symptomatic hip when compared to the asymptomatic hip and to controls, bilateral hip abductor weakness was identified in individuals with GT when compared to controls. The primary functional role of the hip abductor muscles is to maintain alignment of the pelvis in the frontal plane during single leg loading. Given that single leg stance (SLS) is often assessed visually by clinicians to evaluate hip abductor function, Study 2 aimed (1) to quantify trunk, pelvic and hip kinematics in preparation for, and during, a SLS task in those with and without GT, and (2) evaluate the effect of hip abductor muscle strength on these kinematics. Results from Study 2 showed that in contrast to pain-free controls, individuals with GT exhibit greater lateral translation of the pelvis and hip adduction in preparation for SLS; and more hip adduction and less pelvic elevation during SLS. Hip abductor strength appeared to be a key determinant of these kinematic differences, as when adjusting for strength in our analysis only between-group differences in lateral pelvic shift persisted. As altered kinematics of the hip and pelvis were identified in SLS, and walking is a typically provocative functional single leg loading task for those with GT, Study 3 aimed to evaluate kinematics and kinetics of the trunk, hip and pelvis during walking gait. This was the first study to evaluate walking kinematics and kinetics in individuals with GT using three-dimensional gait analysis. Results showed that, in contrast to pain-free controls, individuals with GT exhibited a greater external hip adduction moment throughout the stance phase of walking as well as greater contralateral trunk lean at the time of the first peak hip adduction moment and greater contralateral pelvic drop at the time of the second peak hip adduction moment. Contralateral pelvic drop was significantly correlated with the first and second peak hip adduction moments, and hip adduction angle with the second peak hip adduction moment in those with GT, providing some insight into potential modifiable kinematic patterns underpinning their greater external hip adduction moment. Finally, post-hoc analysis identified two subgroups with opposite trunk and pelvic strategies within the GT group. Taken together, these findings suggest that evaluation of the trunk and pelvis during clinical observation of gait is warranted in order to identify specific maladaptive gait patterns. A greater external hip adduction moment, identified in Study 3, infers a greater demand on the hip abductor muscles, including the gluteus medius and minimus muscles and the overlying muscles that insert into the iliotibial band (ITB). On this basis Study 4 aimed to evaluate the independent and synergistic characteristics of hip abductor muscle activation during walking using electromyography (EMG). This study highlighted altered muscle activity in the posterior gluteus minimus and middle gluteus medius muscle segments during stance phase in individuals with GT, characterized by greater activity continued into mid-stance, compared to controls. Further to this, individuals with GT exhibited less within-participant variability of the posterior gluteus minimus and less between-participant variability in the anterior gluteus minimus and medius segments and upper gluteus maximus when compared to controls. For both groups, synergy analysis identified two muscle synergies during the stance phase of gait. However, differing levels of contribution from the tensor fascia lata muscle to each synergy was observed between those with and without GT. Taken with a greater external hip adduction moment, modified distribution of activity within the gluteal muscle segments and the tensor fascia lata, which generates tension in the ITB via it’s insertion, has the potential to modify gluteal tendon loading. Compressive forces from the tension in the overlying ITB and the greater trochanter below on the gluteal tendons could have potentially negative tendon effects. Lastly, Study 5 investigated kinematics and kinetics of the trunk, hip and pelvis during a step up task. Similar, to the findings of Study 3, parameters of the external hip adduction moment were consistently greater in those with GT during the stance phase of stair ascent. Based on the patterns of the external hip adduction moment, three subgroups were identified in both the GT and control groups, with individuals with GT 4.5 times more likely to have an external hip adduction moment characteristic of a large impulse, greater lateral pelvic translation and less pelvic obliquity at heel strike than the subgroup most likely to contain controls. The studies outlined in this thesis are the first to report strength, kinematic, kinetic and EMG findings in individuals with symptomatic GT in contrast to pain-free controls. Differences were identified in: hip abductor strength; kinematics during SLS, gait and step up tasks; kinetics during walking and step up; and neuromuscular control of the hip abductor muscles during walking. These findings imply that the gluteal tendons might be experiencing modified tensile and compressive loads in those with GT, with implications for tendon health. Given the cross-sectional study design it is not possible to determine whether these differences preceded or followed GT, but it is possible that restoration of muscle strength and normal kinematics may be beneficial for recovery. However future research is needed to determine whether altered muscle activity, kinematics and kinetics can be changed with conservative treatment and subsequent effects on patient outcomes.
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ItemHip joint neuromuscular control and biomechanics in individuals with symptomatic femoroacetabular impingement( 2016)Femoroacetabular impingement (FAI) is recognised as a significant clinical problem among younger active adults. This morphological hip disorder can cause joint stiffness, hip and/or groin pain, and impaired function. Importantly, a link has been proposed between FAI and the future development of hip osteoarthritis. Current treatment often involves arthroscopic surgery; however, there is an overwhelming absence of evidence for its efficacy. It is plausible that non-operative treatments have an important role to play in management of symptomatic FAI. Developing and informing these treatments relies on an objective understanding of the exact nature of the associated physical impairments. This thesis aimed to comprehensively understand the extent of current knowledge and provide new data of the neuromuscular and biomechanical impairments in individuals with symptomatic FAI. Study 1 clarifies the current understanding of physical impairments and activity limitations in individuals with FAI by way of systematic review with consideration of study quality. This review identified 16 studies of level 3b-4 evidence that reported some physical impairments when compared to individuals without FAI. These were mainly in the domain of hip range of motion, particularly in directions of impingement (deep flexion, combined with adduction and internal rotation). Other impairments were suggested during gait, squatting, stair climbing and isometric muscle contractions, though evidence was limited and conflicting. Importantly, surgery for FAI was shown to restore some, but not all, physical impairments. This systematic review identified a need for studies to assess whether hip range of motion and neuromuscular function are compromised in dynamic tasks designed to target positions of impingement in individuals with symptomatic FAI. On the basis of recommendations from Study 1, cross-sectional investigations comparing several biomechanical and neuromuscular factors in individuals with symptomatic FAI, diagnosed by clinical examination and imaging features (n=15), to a matched asymptomatic control group, with no evidence of morphological FAI (n=15) were undertaken. Tri-planar hip kinematics and kinetics during gait were compared between the two groups in Study 2. Individuals with FAI walked with less range of motion in the sagittal plane during a gait cycle, but did not exhibit any other impairments. Less within-group variability was also observed in the FAI group at peak hip adduction angle and peak hip internal rotation angle (directions of impingement) during stance. On the foundation that conservative treatments and rehabilitation protocols following surgery for FAI regularly include hip muscle strengthening, Study 3 compared isometric and isokinetic hip muscle strength and agonist/antagonist ratios between the two groups. Individuals with FAI demonstrated isometric hip abductor muscle weakness, and a strength imbalance in the hip rotators when measured isometrically, but not isokinetically. As no studies have previously explored deep hip muscle function in individuals with symptomatic FAI, Study 4 investigated potential differences in muscle synergies during gait between the two groups. A non-negative matrix factorization algorithm extracted three synergies from the electromyographic patterns of select deep hip muscles, measured using intramuscular electrodes. Between-group comparison indicated the variance accounted for by the muscle synergies was higher in the FAI group than the pain-free controls. This suggests that coordination of deep hip muscles with the anatomical capacity to oppose impingement differed between groups, and importantly, that this difference can be attributed to increased variability in the healthy controls. Participants with FAI exhibited a more homogeneous pattern during the early swing phase of gait that appeared to be consistent with an effort to increase hip joint stability. Given that abnormal hip joint function was not well defined with gait assessment alone, Study 5 compared hip and pelvis biomechanics during two, more provocative, squatting tasks. Findings demonstrated that individuals with symptomatic FAI can squat to a depth comparable to controls, regardless of squatting task design. However, biomechanical alterations were evident at the hip and pelvis when the task was constrained. Decreased variability was once again demonstrated in the FAI group with respect to the transverse plane hip angle during the constrained task. The studies outlined in this thesis identified new neuromuscular and biomechanical impairments in individuals with symptomatic FAI. Taken together, these findings imply that FAI patients have adopted a motor coordination strategy that is consistently similar to each other, a feature that is not observed in healthy pain-free individuals with no pathology. Given the cross-sectional study design, it is not possible to clarify whether the differences precede or follow pathology development. Clinical interventions to restore normal musculoskeletal function around the hip joint may be beneficial, but future research is needed to determine whether these features can be changed and whether this improves outcomes.
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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.
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ItemGait analysis methods to minimise soft tissue artefact and evaluate techniques to locate the hip joint centre( 2010)The purpose of this thesis was to investigate gait analysis methods used to minimise soft tissue artefact (STA) when measuring the kinematics and kinetics of human gait. STA affects all gait analysis methods and is considered to be one of the major sources of error in clinical motion analysis. A systematic review was initially performed to quantify the magnitude of STA for different areas of the lower limbs during gait analysis. Despite the high quality of the existing literature, the results of the review were inconclusive regarding the exact magnitude of STA during human gait analysis. Previously, there were no methods used consistently throughout the reviewed studies to assess STA. The primary aim of this thesis was to determine the most valid method for minimising STA during human gait analysis. Whilst the systematic review provided equivocal results on the magnitude of STA, it was able to confirm that STA at the tibia is less than for the femur segment. As a result, the tibial segment was investigated to determine marker locations that are least susceptible to STA. Twenty unimpaired young adults were included in the study and were instrumented with 36 markers, including 10 markers on each shank segment. The markers were well spread across the tibial segment in order to assess as many locations as possible. Four markers located on the tibia were less susceptible to STA. These were the proximal and distal anterior tibial crest markers as well as the medial and lateral malleolar markers. These markers were rigid to one another thus were rigid to the underlying bone. In order to assess the modelling methods proposed in the literature a gold standard comparison was required. A potential new gold standard method was identified as 3-D freehand ultrasound (3-DUS). This was believed to be a non-invasive and cost effective method for locating internal bony structures. A validation of the new method (3-DUS) against MRI was performed to ensure the new gold standard was a valid methodology. The two methods, 3-DUS and MRI were compared for their accuracy in determining the location of the HJC within the pelvis segment. Twenty unimpaired participants were included in this study. The participants were of variable ages and physical composition. The difference between 3-DUS and MRI determined distance between the left and right HJC was 4.0 ± 2.3mm. It was determined that the results from 3-DUS were clinically not significantly different to MRI. The results of this investigation indicated that 3-DUS could be used as a gold standard measurement for three dimensional gait analysis (3-DGA) research. The new gold standard method was used to validate existing 3-DGA modelling methods to determine which obtained the most accurate location of the HJC. To date, the greatest clinical application for gait analysis is as a test for people with central nervous system disorders associated with spasticity, especially children with cerebral palsy (CP) (Simon 2004). For this reason, 53 patients with gait abnormalities who had been referred to the Royal Children’s Hospital gait laboratory for a 3-DGA were tested. The participant sample represented patients who were referred to the Hugh Williamson Gait Analysis Laboratory (HWGAL). This was apparent because from 2008-2009 69% of patients at HWGAL had a diagnosis of CP, of the sample included in this study, 67% had a CP diagnosis. Patients underwent a 3-DGA in addition to a 3-DUS of their left and right femoral heads. Resultant ultrasounds were assessed for the quality of the images and 46 patients were included for data analysis. Seven different methods were investigated for the determination of the HJC and four of these were analysed in two different ways, as such there were 11 models compared to 3-DUS. The Harrington et al method obtained the most accurate and repeatable results where the 3-D location error was 14.3 ± 8.0mm. That method considerably outperformed the functional techniques that had previously been proposed in the literature. This highlighted the importance of testing research techniques in target populations. To conclude, this thesis has identified locations on the tibia which are most rigid to the underlying bone as well as a new gold standard measurement tool suitable for use in 3-D gait analysis research. The thesis has also demonstrated the validity of using functional methods for determining the HJC in pathological populations. Limitations of previous research were identified, including a lack of translation of research findings into clinical practice. Future work following on from this thesis should aim to address this issue.