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OBJECTIVE: To investigate the effect of progressive resistance exercise compared with low-intensity home-based exercises on knee-muscle strength and joint function in people with anterior cruciate ligament (ACL) reconstruction and persistent hamstring strength deficits at 12–24 months after surgery. DESIGN: Randomized controlled superiority trial with parallel groups, balanced randomization (1:1), and blinded outcome assessment. METHODS: People with ACL reconstruction (hamstring autograft) and persistent hamstring muscle strength asymmetry were recruited 1 to 2 years postsurgery and randomized to either 12 weeks of supervised progressive strength training (SNG), or 12 weeks of home-based, low-intensity exercises (CON). The primary outcome was between-group difference in change in maximal isometric knee flexor muscle strength at 12-week follow-up. RESULTS: Fifty-one participants (45% women, 27 ± 6 years) were randomized to SNG (n = 25) or CON (n = 26), with 88% follow-up rate at 12 weeks. People in the SNG group improved their knee flexor muscle strength (0.18 N·m/kg, 95% confidence interval [CI]: 0.07, 0.29; P = .002) more than the CON group, from baseline to 12 weeks. The SNG group also had superior Knee Injury and Osteoarthritis Outcome Scores for Pain (4.6, 95% CI: 0.4, 8.7; P = .031) and daily living function (4.7, 95% CI: 1.2, 8.2; P = .010) compared to the CON group. CONCLUSION: In people with persistent hamstring muscle strength deficits after ACL reconstruction, 12 weeks of supervised progressive strength training was superior to low-intensity home-based exercises for improving maximal knee flexor muscle strength and some patient-reported outcomes. J Orthop Sports Phys Ther 2023;53(1):40–48. Epub: 17 October 2022. doi:10.2519/jospt.2022.11360

Background People with Parkinson’s disease (PD) are at a high risk of falls, with ~ 60% experiencing a fall each year. Greater mediolateral head and pelvis motion during gait are known to increase the risk of falling in PD, however the ability to modify these aspects of gait has not been examined. Thus, this study aimed to examine whether mediolateral trunk, head and pelvis motion during walking could be successfully decreased in people with PD using real-time biofeedback. Methods Participants were provided with real-time biofeedback regarding their mediolateral trunk lean via a visual projection whilst walking along an 8-m indoor walkway. Using the feedback provided, they were asked to reduce the magnitude of their mediolateral trunk lean. Gait was recorded for four conditions (i) Baseline, (ii) Intervention, (iii) immediately Post-Intervention, and (iv) 1-week Follow-Up. Biomechanical variables associated with falls risk were compared between conditions, including normalised mediolateral motion, gait velocity and stride length. Results A reduction in mediolateral trunk lean, step length and gait velocity from Baseline to the Intervention and Post-intervention conditions was observed. Contrary to this, increased normalised ML pelvis and trunk motion was observed between the Baseline and Intervention conditions, but returned to Baseline levels in the Post-Intervention condition. Conclusions Results from the current study suggest that real-time visual biofeedback may be effective at modifying specific gait characteristics that are associated with falls in PD. Further research is required to better understand the influence of this intervention approach on falls incidence. Trial registration Australian New Zealand Clinical Trials Registry ACTRN12620000994987. Registered 10 June 2020 - Retrospectively registered, https://anzctr.org.au/Trial/Registration/TrialReview.aspx?id=380324

Background Metronome cueing has been shown to reduce gait variability and thereby potentially reduce falls risk in individuals with Parkinson’s disease. It is unclear however, if metronome cueing has a similar effect in healthy older adults with a history of falls. Aim To investigate whether a traditional and/or an adaptive metronome, based on an individual’s gait pattern, were effective in reducing gait variability in older adults with a history of falls. Methods Twenty older adults (15 women, 71 ± 4.9 years) with a history of falls were included in this cross-over study. Participants received two types of cueing (adaptive and traditional metronome) 1 week apart. The variability of the participants’ stride time, stride length, walking speed and duration of double leg support were recorded during three walking conditions (baseline, during feedback and post-feedback gait). Repeated-measures ANOVA was used to assess the possible effects of the two cueing strategies on gait variables. Results Compared with the baseline condition, participants had significantly increased stride time variability during feedback (F (2) = 9.83, p F (2) 3.69, p = 0.034). Increased stride time variability was observed with the adaptive metronome in comparison to the traditional metronome. Conclusion Metronome cueing strategies may reduce double leg support variability in older adults with a history of falls but seem to increase stride time variability. Further studies are needed to investigate if metronome cueing is more beneficial for individuals with greater baseline gait variability than those included in the current study.

Objectives: There is limited research on sex differences in postural orientation (ie, alignment between body segments) in people with knee injury measured with a clinically applicable method. An understanding of the relationship between postural orientation and physical function may help guide decision making in rehabilitation. The aims were to evaluate (1) sex differences in visual assessment of Postural Orientation Errors (POEs) and (2) the association between POEs and objective and patient-reported physical function, in men and women with anterior cruciate ligament reconstruction (ACLR). Methods: Twenty-four women and 29 men (mean 26.7 (SD 6.5) years) with ACLR were included. Six POEs (lower extremity and trunk) were scored from a video of five tasks with varying difficulty to compute POE scores (total and subscores). Objective physical function was evaluated with the single-leg hop for distance and side hop. Patient-reported physical function was evaluated using patient-reported outcome measures (PROMs). Results: Women had significantly more POEs than men (median difference 5.5-25, p≤0.028). More POEs were associated with shorter hop distance and fewer side hops in women (r s = -0.425 to -0.518, p0.05). No associations were found between POE scores and PROMs, in either sex (r s < -0.246, p>0.05). Conclusions: Women with ACLR seem to have more POEs compared with men, indicating worse postural orientation. More POEs were associated with worse hop performance, suggesting that POE scores may be used as criteria for rehabilitation progression. The lack of associations between POE scores and PROMs indicate that these measures complement each other.

Background To systematically review the association between knee abduction kinematics and kinetics during weight-bearing activities at baseline and the risk of future anterior cruciate ligament (ACL) injury. Methods Systematic review and meta-analysis according to PRISMA guidelines. A search in the databases MEDLINE (PubMed), CINAHL, EMBASE and Scopus was performed. Inclusion criteria were prospective studies including people of any age, assessing baseline knee abduction kinematics and/or kinetics during any weight-bearing activity for the lower extremity in individuals sustaining a future ACL injury and in those who did not. Results Nine articles were included in this review. Neither 3D knee abduction angle at initial contact (Mean diff: -1.68, 95%CI: − 4.49 to 1.14, ACL injury n = 66, controls n = 1369), peak 3D knee abduction angle (Mean diff: -2.17, 95%CI: − 7.22 to 2.89, ACL injury n = 25, controls n = 563), 2D peak knee abduction angle (Mean diff: -3.25, 95%CI: − 9.86 to 3.36, ACL injury n = 8, controls n = 302), 2D medial knee displacement (cm; Mean diff:: -0.19, 95%CI: − 0,96 to 0.38, ACL injury n = 72, controls n = 967) or peak knee abduction moment (Mean diff:-10.61, 95%CI: - 26.73 to 5.50, ACL injury n = 54, controls n = 1330) predicted future ACL injury. Conclusion Contrary to clinical opinion, our findings indicate that knee abduction kinematics and kinetics during weight-bearing activities may not be risk factors for future ACL injury. Knee abduction of greater magnitude than that observed in the included studies as well as factors other than knee abduction angle or moment, as possible screening measures for knee injury risk should be evaluated in future studies.

Objective Undesirable postural orientation may be a risk factor for a second anterior cruciate ligament (ACL) injury. The purpose of this study was to evaluate face validity, internal consistency, and interrater reliability of an extended version of a previous test battery for visual assessment of postural orientation errors (POEs) in patients during the late phase of rehabilitation following ACL reconstruction (ACLR) (ie, when they have initiated jumping exercises). Methods This study used a cross-sectional design. Fifty-three patients (45% women) in the late phase of ACLR rehabilitation performed 5 functional tasks of varying difficulty. POEs of the lower extremity and trunk were visually assessed from video and scored on a scale from 0 (good) to 2 (poor). Results The side-hop and 2 new POEs (femur medial to shank, femoral valgus) were added to the test battery after expert focus group discussions. Internal consistency was calculated for all tasks (α = .712–.823). Interrater reliability showed fair to substantial agreement for femur medial to shank and femoral valgus during all tasks (K = 0.31–0.815) and almost perfect agreement for side-hop (intraclass correlation coefficient = 0.88). Conclusions The good internal consistency and reliability after adding side-hop, femur medial to shank, and femoral valgus suggests that this test battery is a suitable tool to quantify postural orientation throughout ACLR rehabilitation. Impact This test battery for visual assessment of POEs was evaluated in a heterogeneous group of patients in different phases of ACLR battery and can be used in clinical practice to measure POEs in patients with ACLR, including in the late phase of rehabilitation to return to sport. This study encourages research on more demanding tasks and additional POEs to cover the entire rehabilitation period after ACL injury or reconstruction.

Study Design Cross-sectional study. Background Visual rating of postural orientation during functional tasks may be a valuable tool to track rehabilitation progress following anterior cruciate ligament (ACL) injury. A valid test battery assessing postural orientation as a separate construct is lacking. Objectives To evaluate measurement properties of a test battery to assess postural orientation in patients with ACL injury. Methods The content validity of functional tasks was assessed by expert focus group discussions. Fifty-one patients (45% women) with ACL injury performed 9 functional tasks of varying difficulty. Interpretability, internal consistency, interrater reliability, and measurement error were assessed for segment-specific postural orientation errors (POEs), within-task POEs, and total POE score. Postural orientation errors were scored on video on an ordinal scale from 0 (no POEs) to 3 (major POEs). Results Stair ascent, deep squat, and crossover hop for distance were excluded in focus group discussions. Postural orientation errors in some tasks were excluded due to floor effects. The mini-squat and drop jump were excluded due to poor internal consistency (α≤.184). Interrater reliability values for segment-specific POEs and within-task POEs yielded fair to almost perfect agreement (κ = 0.429-0.875) and almost perfect agreement for total POE score (intraclass correlation coefficient = 0.842), without systematic differences between raters. The smallest detectable changes were 0.7 and 5 points for groups and individuals, respectively. Conclusion The final test battery (single-leg mini-squat, stair descent, forward lunge, single-leg hop for distance) of 4 POEs (foot pronation, medial knee-to-foot position, hip joint POEs, and trunk segment POEs) demonstrated good measurement properties in people with ACL injury. J Orthop Sports Phys Ther 2017;47(11):863-873. doi:10.2519/jospt.2017.7270.

Objectives To investigate if frontal plane kinematics are predictive of three dimensional (3D) hip adduction and hip internal rotation during running. Study design Cross-sectional. Setting Biomechanics laboratory. Participants Thirty healthy male runners aged 18–45 years. Main outcome measures Two dimensional (2D) angles in the frontal plane (peak pelvic obliquity, peak hip adduction, peak femoral valgus, peak knee valgus and peak tibial valgus) and 3D hip adduction and hip internal rotation during stance phase of running were obtained. Results Linear regression modelling revealed that peak 2D pelvic obliquity (a drop towards the contralateral leg) and peak femoral valgus significantly predicted 88% of the variance in peak 3D hip adduction (p < 0.001). Frontal plane kinematics however, were not predictive of peak hip internal rotation in 3D (p > 0.05). Conclusions Frontal plane kinematics, specifically contralateral pelvic drop and femoral valgus, predicted the vast majority of the variance in 3D hip adduction during the stance phase of running. This indicates that 2D video may have potential as a clinically feasible proxy for measurement of peak 3D hip adduction – a risk factor for patellofemoral pain.

Objectives To systematically review measurement properties of visual assessment and rating of Postural Orientation Errors (POEs) in participants with or without lower extremity musculoskeletal disorders. Methods A systematic review according to the PRISMA guidelines was conducted. The search was performed in Medline (Pubmed), CINAHL and EMBASE (OVID) databases until August 2016. Studies reporting measurement properties for visual rating of postural orientation during the performance of weight-bearing functional tasks were included. No limits were placed on participant age, sex or whether they had a musculoskeletal disorder affecting the lower extremity. Results Twenty-eight articles were included, 5 of which included populations with a musculoskeletal disorder. Visual rating of the knee-medial-to-foot position (KMFP) was reliable within and between raters, and meta-analyses showed that this POE was valid against 2D and 3D kinematics in asymptomatic populations. Other segment-specific POEs showed either poor to moderate reliability or there were too few studies to permit synthesis. Intra-rater reliability was at least moderate for POEs within a task whereas inter-rater reliability was at most moderate. Conclusions Visual rating of KMFP appears to be valid and reliable in asymptomatic adult populations. Measurement properties remain to be determined for POEs other than KMPF.

Arthroscopic partial meniscectomy (APM) may lead to changes in underlying trabecular bone (TB) structure potentially promoting the development of knee joint osteoarthritis. Our aim was to investigate if there are early changes occurring in tibial subchondral TB texture in the leg undergoing medial APM compared with the unoperated non-injured contra-lateral leg. The bone texture was measured as the medial-to-lateral ratio of fractal dimensions (FD) calculated for regions selected on weight-bearing anteroposterior tibiofemoral x-rays. Twenty-one subjects before and 12 months after APM were included from 374 patients scheduled for unilateral medial APM. The medial-to-lateral ratio was calculated for horizontal, vertical, and roughest FDs respectively. Higher FD means higher bone roughness. Each FD was calculated over a range of scales using a variance orientation transform method. Mean values of medial-to-lateral horizontal FD calculated for APM knees at follow-up were higher than those at baseline. For unoperated knees the values were lower. The difference in the horizontal FD change from baseline to follow-up between APM and contra-lateral legs was 0.028 (95% CI, 0.004-0.052). The bone roughness changes may reflect the increase in peak knee adduction moment (KAM) and KAM impulse during walking reported for the same cohort in a previous study. They may also reflect early signs of osteoarthritis development and thus, we speculate that individuals with increased bone texture roughness ratio after APM might be at higher risk of knee osteoarthritis development.

Background: Patients with a meniscal tear are frequently treated with arthroscopic partial meniscectomy (APM) which may alter the net extension moment across the entire lower limb – known as the total support moment (TSM).Purpose: To investigate changes in TSM during walking in patients undergoing APM.Methods: Three-dimensional motion analysis of walking was performed in individuals with meniscal tear prior to APM and 12 months after. Peak TSM, positive ankle (ASM), knee (KSM), and hip (HSM) moments at the time of peak TSM were calculated together with corresponding angular impulses. Results: Patients (n = 20) were middle aged (45.9 ± 6.3 years) and the majority male (70%). At baseline a lower KSM (mean [95%CI]; 0.59 Nm/BM ∙ HT% [-1.93; 3.11], P = 0.048) and a trend towards lower peak TSM (0.46 Nm/BM ∙ HT% [-1.82; 2.78], P = 0.099) were observed for the APM leg compared with the contralateral. Pre- versus post-APM change scores indicated a relative decrease in loading of the contralateral leg for peak TSM (-0.49 Nm/BM ∙ HT% [-0.96; -0.01], P = 0.047) and a trend towards a relative increase in loading of the APM leg for peak KSM (-0.41 Nm/BM ∙ HT% [-0.92; 0.09], P = 0.105). No differences were observed in angular impulse variables.Conclusions: Prior to APM a strategy to unload the injured knee was manifested by reduced KSM and a tendency to a reduced peak TSM. A more equal distribution of joint moments between injured and contralateral legs was observed 12 months following APM.

Background Increased knee abduction during weight-bearing activities is suggested to be a contributing factor for the high knee injury risk reported in women. However, studies investigating gender difference in knee abduction are inconclusive. Objective To systematically review gender-differences in knee abduction during weight-bearing activities in individuals with or without knee injury. Methods A systematic review and meta-analysis were conducted according to the PRISMA guidelines. A search in the databases Medline, CINAHL and EMBASE was performed until September 2015. Inclusion criteria were studies that reported (1) gender differences, (2) healthy individuals and/or those with anterior cruciate ligament (ACL) deficiency or reconstruction or patellofemoral pain PFP, and (3) knee abduction assessed with either motion analysis or visual observation during weight-bearing activity. Results Fifty-eight articles met the inclusion criteria. Women with PFP had greater peak knee abduction compared to men (Std diff in mean; −1.34, 95%CI; −1.83 to −0.84). In healthy individuals, women performed weight-bearing tasks with greater knee abduction throughout the movement (initial contact, peak abduction, excursion) (Std diff in mean; −0.68 to −0.79, 95%CI; −1.04 to −0.37). In subgroup analyses by task, differences in knee abduction between genders were present for most tasks, including running, jump landings and cutting movements. There were too few studies in individuals with ACL injury to perform meta-analysis. Conclusion The gender difference in knee abduction during weight-bearing activities should be considered in training programs aimed at preventing or treating knee injury.

Objective: To investigate if muscle strength and muscle activation patterns are associated with increased knee abduction during two functional tasks, commonly used in rehabilitation for individuals with anterior cruciate ligament reconstruction (ACLR).Design: Cross-sectional study.Setting: Laboratory.Participants: 24 women and 29 men approximately 7 months after ACLR. Main Outcome Measures: Isometric peak torque of the trunk and lower extremity muscles were determined during maximal voluntary contractions. Trunk and lower extremity average muscle activation amplitude and peak knee abduction were evaluated during the single-leg squat (SLS) and the single-leg hop for distance (SLHD) for the injured side. Separate backward regressions were performed for men and women.Results: In women, lower knee flexion and extension strength were associated with greater peak knee abduction during the SLS (B= 4.63 – 18.26, p≤0.036); lower knee flexion strength and iliocostalis activation on the non-injured side were associated with greater peak knee abduction during the SLHD (B= 0.60 – 20.48, p≤0.043). No associations between muscle function and peak knee abduction were found in men.Conclusions: Muscle function may contribute differently to knee abduction in men and women after ACLR. This should be considered when designing rehabilitation programs to reduce knee abduction in these patients.

Introduction Given the high rate of falls during walking in people with idiopathic Parkinson's disease (PD), identifying at risk individuals and developing targeted interventions to reduce falls incidence is paramount. Numerous studies have investigated gait-related risk factors for falls in PD, however findings are inconsistent across studies, and thus a synthesis of the current evidence is needed to guide clinical practice and the development of interventions to reduce falls risk. The objective of this study was to systematically review the literature regarding the association between walking biomechanics and falls in people with PD, and where possible, perform meta-analyses. Methods The study was performed in accordance with the PRISMA guidelines. Databases were searched until January 2018 to identify articles that reported on the association between walking biomechanics and prospective or retrospective falls in people with PD. Results Twenty-six articles were included (15 prospective studies, 11 retrospective studies). Articles reported on spatiotemporal and kinematic characteristics, and muscle activation patterns. Meta-analyses revealed slower walking speed, lower cadence, shorter strides and more mediolateral head and pelvis motion in those at higher risk of future falls. Findings from prospective and retrospective articles were largely consistent. Conclusion Our findings identify spatiotemporal and kinematic characteristics of gait that are risk factors for falls in PD. Modification of these characteristics may have the potential to mediate falls risk, and future research to investigate this possibility is merited. The influence of body and ground reaction forces, and muscle activation patterns on falls risk in PD is currently under-researched.

Background Anterior cruciate ligament (ACL) reconstruction, using hamstring auto-graft is a common surgical procedure, which often leads to persistent hamstring muscle-strength deficiency and reduced function. The purpose of this randomized controlled trial (RCT) is to investigate the effect of a combined, progressive, strength and neuromuscular exercise intervention on knee muscle strength, functional capacity and hamstring muscle-tendon morphology in ACL-reconstructed patients with persistent hamstring muscle-strength deficiency compared with controls. Methods/design The study is designed as a multicenter, parallel-group RCT with balanced randomization (1:1) and blinded outcome assessments (level of evidence: II) and will be reported in accordance with the CONSORT Statement. Fifty ACL-reconstructed patients (hamstring auto-graft) with persistent limb-to-limb knee-flexor muscle-strength asymmetry at 12–24 months’ post surgery, will be recruited through outpatient clinics and advertisements. Patients will be randomized to a 12-week progressive, strength and neuromuscular exercise group (SNG) with supervised training twice weekly or a control intervention (CON) consisting of a home-based, low-intensity exercise program. Outcome measures include between-group change in maximal isometric knee-flexor strength (primary outcome) and knee-extensor muscle strength, hamstring-to-quadriceps strength ratios of the leg that has been operated on and Knee injury and Osteoarthritis Outcome Score (KOOS) (secondary outcomes). In addition, several explorative outcomes will be investigated: The International Knee Documentation Committee Subjective Knee Form (IKDC), the Tegner Activity Score, rate of force development (RFD) for the knee flexors and extensors, tendon regeneration and potential muscle hypertrophy at graft harvest site evaluated by magnetic resonance imaging (MRI), postural control, kinetic/kinematic gait characteristics and knee-related functional capacity. Discussion This RCT is designed to investigate the effect of combined, progressive-resistance and neuromuscular exercises on knee-flexor/extensor strength, in the late rehabilitation phase following ACL reconstruction. Reduced hamstring strength represents a potential risk factor for secondary ACL rupture and accelerated progression of osteoarthritis. If deemed effective, the intervention paradigm introduced in this study may help to improve current treatment strategies in ACL-reconstructed patients. Trial registration ClinicalTrials.gov, ID: NCT02939677 (recruiting). Registered on 20 October 2016. Electronic supplementary material The online version of this article (10.1186/s13063-018-2448-3) contains supplementary material, which is available to authorized users.

Study Design Cross-sectional study. Background Visual rating of postural orientation during functional tasks may be a valuable tool to track rehabilitation progress following anterior cruciate ligament (ACL) injury. A valid test battery assessing postural orientation as a separate construct is lacking. Objectives To evaluate measurement properties of a test battery to assess postural orientation in patients with ACL injury. Methods The content validity of functional tasks was assessed by expert focus group discussions. Fifty-one patients (45% women) with ACL injury performed 9 functional tasks of varying difficulty. Interpretability, internal consistency, interrater reliability, and measurement error were assessed for segment-specific postural orientation errors (POEs), within-task POEs, and total POE score. Postural orientation errors were scored on video on an ordinal scale from 0 (no POEs) to 3 (major POEs). Results Stair ascent, deep squat, and crossover hop for distance were excluded in focus group discussions. Postural orientation errors in some tasks were excluded due to floor effects. The mini-squat and drop jump were excluded due to poor internal consistency (α≤.184). Interrater reliability values for segment-specific POEs and within-task POEs yielded fair to almost perfect agreement (κ = 0.429-0.875) and almost perfect agreement for total POE score (intraclass correlation coefficient = 0.842), without systematic differences between raters. The smallest detectable changes were 0.7 and 5 points for groups and individuals, respectively. Conclusion The final test battery (single-leg mini-squat, stair descent, forward lunge, single-leg hop for distance) of 4 POEs (foot pronation, medial knee-to-foot position, hip joint POEs, and trunk segment POEs) demonstrated good measurement properties in people with ACL injury. J Orthop Sports Phys Ther 2017;47(11):863-873. doi:10.2519/jospt.2017.7270.

Objective To investigate the acute effect of gait retraining aimed at reducing tibial peak positive acceleration (PPA) on energetic cost (VO 2 ). Design Intervention with a pre/post-test design. Setting University biomechanics laboratory. Participants 12 healthy male runners (23.4 ± 5.3 years, 179.7 ± 4.3 cm, 75.6 ± 9.2 kg). Main outcome measures Tibial PPA and oxygen consumption (VO 2 ) were measured after a five minute baseline run and at the end of a gait retraining session aimed at minimizing tibial PPA. Results Tibial PPA significantly decreased between baseline and after gait retraining (32.6%, p = 0.007). VO 2 significantly increased between the two time periods (9.3%, p = 0.008). There was no correlation between change in tibial PPA and change in VO 2 (p = 0.956, r = 0.018). Conclusion Practitioners who aim to reduce injury risk by minimizing tibial PPA in runners need to consider the possible acute effect on performance as a result of changes in VO 2 . Further investigation is warranted to understand the energetic cost of different kinematic strategies used by individuals.

Purpose: The purpose of this study was to compare the neuromotor control of the gluteus medius (GMED) and gluteus maximus (GMAX) muscles in runners with Achilles tendinopathy to that of healthy controls. Methods: Fourteen male runners with Achilles tendinopathy and 19 healthy male runners (control) ran overground while EMG of GMED and GMAX was recorded. Three temporal variables were identified via visual inspection of EMG data: (i) onset of muscle activity (onset), (ii) offset of muscle activity (offset), and (iii) duration of muscle activity (duration). A multivariate analysis of covariance with between-subject factor of group (Achilles tendinopathy, control) and variables of onset, offset, and duration was performed for each muscle. Age, weight, and height were included as covariates, and α level was set at 0.05. Results: The Achilles tendinopathy group demonstrated a delay in the activation of the GMED relative to heel strike (P < 0.001) and a shorter duration of activation (P < 0.001) compared to that of the control group. GMED offset time relative to heel strike was not different between the groups (P = 0.063). For GMAX, the Achilles tendinopathy group demonstrated a delay in its onset (P = 0.008), a shorter duration of activation (P = 0.002), and earlier offset (P < 0.001) compared to the control group. Conclusions: This study provides preliminary evidence of altered neuromotor control of the GMED and GMAX muscles in male runners with Achilles tendinopathy. Although further prospective studies are required to discern the causal nature of this relationship, this study highlights the importance of considering neuromotor control of the gluteal muscles in the assessment and management of patients with Achilles tendinopathy.

Background High mechanical loading has been consistently linked with medial tibiofemoral osteoarthritis, and is considered to play a central role in the pathogenesis of the disease. Evidence from healthy adults indicates that knee flexion kinematics may influence knee load. The purpose of this study therefore, was to investigate the association between knee flexion kinematics and indicators of joint loading during walking (peak moments and vertical ground reaction force), in individuals with medial tibiofemoral osteoarthritis. Methods In this cross-sectional study, 89 participants with painful medial tibiofemoral osteoarthritis completed three-dimensional walking gait analysis to measure stance phase ground reaction forces, knee joint moments, and knee flexion kinematics. Findings In stepwise regression, greater knee flexion excursion was associated with higher peak vertical ground reaction force, accounting for 10% of its variance (B = 0.62 [95% CI 0.34, 0.89], P < 0.001). Greater peak knee flexion was associated with a higher flexion moment, accounting for 44% of its variance (B = 0.12 [95% CI 0.09, 0.15], P < 0.001). No association was found between the knee adduction moment and knee flexion kinematics during walking. Interpretation Our data suggest that greater knee flexion is associated with higher joint loads in the sagittal plane (i.e. a higher peak knee flexion moment). However, knee flexion kinematics were not associated with the knee adduction moment — a proxy measure of medial compartment knee load. Thus, high knee flexion should be considered an undesirable gait characteristic with respect to knee load in individuals with medial tibiofemoral osteoarthritis.

Purpose: Achilles tendinopathy (AT) is a prevalent injury in running sports. Understanding the biomechanical factors associated with AT will assist in its management and prevention. The purpose of this study was to compare hip and ankle kinematics and kinetics in runners with and without AT. Methods: Fourteen male runners with AT and 11 healthy male runners (CTRL) ran over ground while lower-limb joint motion and ground reaction force data were synchronously captured. Hip and ankle joint angles, moments, and impulses in all three planes (sagittal, transverse, and frontal) were extracted for analysis. Independent t-tests were used to compare the differences between the AT and the CTRL groups for the biomechanical variables of interest. After Bonferroni adjustment, an alpha level of 0.0026 was set for all analyses. Results: The AT group exhibited an increased peak hip external rotation moment (P = 0.001), hip external rotation impulse (P < 0.001), and hip adduction impulse (P < 0.001) compared with the CTRL group. No significant differences in ankle biomechanics were observed. Conclusion: This study presents preliminary evidence indicating that male runners with AT display altered hip biomechanics with respect to their healthy counterparts. Because of the retrospective design of the study, it is unknown whether these alterations are a predisposing factor for the disorder, a result of the condition, or a combination of both. The results of this study suggest that optimizing hip joint function should be considered in the rehabilitation of runners with AT.

Background: Increased knee abduction angle during activity is suggested to be a risk factor for sustaining an anterior cruciate ligament (ACL) injury or developing patellofemoral pain syndrome (PFPS). Knowledge of the modifiable mechanisms that are associated with increased knee abduction will aid in the appropriate design of preventive and rehabilitative strategies for these injuries. Objective: Our objective was to systematically review modifiable mechanisms contributing to increased knee abduction in healthy people and in individuals with an ACL injury or PFPS. Methods: We performed a systematic review and meta-analysis according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched the databases MEDLINE, CINAHL, and Embase until September 2015. Inclusion criteria were studies in healthy individuals and/or those with ACL injury or PFPS reporting (1) muscle strength, muscle activation, proprioception, and/or range of motion (ROM) and (2) knee abduction angle assessed with either motion analysis or visual observation during weight-bearing activity. Results: In total, 33 articles were included. Reduced trunk strength, reduced gluteus maximus amplitude, decreased ankle ROM, and increased hip external rotation ROM were moderately associated with increased knee abduction angle (r −0.34 or higher, standardized difference in means (SDM) greater than −0.39, p < 0.05, articles n = 3, total sample size n = 101–114) in healthy individuals. Decreased strength of hip abductors, external rotators, and extensors and knee flexors were at most weakly associated with increased knee abduction angle (r ≤ 0.21, p = 0.013–0.426, articles n = 2–9, total sample size n = 80–311). Too few articles included patients with knee injury to be included in any meta-analysis. Conclusion: The associations identified in this review indicate that investigation of strengthening of the trunk muscles, and improvement of gluteus maximus activation and ankle ROM to change knee kinematics is merited. Studies on modifiable factors associated with increased knee abduction angle in people with knee injury are needed.

Objectives: Reducing tibial acceleration through gait retraining is thought to reduce the risk of stress fracture development, however current approaches require the use of advanced accelerometry equipment not readily available in the clinical setting. The aim was to compare the effect of clinician guided feedback with accelerometry guided feedback on peak tibial accelerations during running.Design: Repeated measures randomised design.Methods: Twenty-two healthy male runners were randomised to receive either tibial accelerometry or clinician guided feedback. Peak tibial accelerations were obtained for all participants (i) prior to intervention, (ii) after 10 min of feedback, (iii) after a further 10 min without feedback, and (iv) 1 week later.Results: Across groups, significant reductions in peak tibial acceleration were observed from baseline to each of the subsequent time points in the order of 19-29% (p = 0.001). No between-group differences in peak tibial acceleration were observed at any of the follow-up time points (p = 0.434).Conclusions: These data indicate that in the short term the low cost, low technology, clinician guided approach to retraining running gait may be equally as effective as the more expensive accelerometry guided solution in reducing peak tibial accelerations. Longer term follow-up is required to evaluate the efficacy of both approaches in reducing the risk of stress fracture development. (C) 2015 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

Creaby MW, Bennell KL, Hunt MA. Gait differs between unilateral and bilateral knee osteoarthritis. Objectives To compare walking biomechanics in the most painful leg, and symmetry in biomechanics between legs, in individuals with (1) unilateral pain and structural osteoarthritis (OA), (2) unilateral pain, but bilateral structural OA, and (3) bilateral pain and structural OA and in (4) an asymptomatic control group. Design Cohort study. Setting Laboratory based. Participants Participants with symptomatic and/or radiographic medial tibiofemoral OA in one or both knees (n=91), and asymptomatic control participants (n=31). Interventions Not applicable. Main Outcome Measure The peak knee adduction moment, peak knee flexion moment, knee varus-valgus angle, peak knee flexion angle, toe-out, and trunk lean were computed from 3-dimensional analysis of walking at a self-selected speed. Results After controlling for walking speed, greater trunk lean toward the more painful knee and reduced flexion in the more painful knee were observed in all OA groups compared with the control group. Between-knee asymmetries indicating greater varus angle and a lower external flexion moment in the painful knee were present in those with unilateral pain and either unilateral or bilateral structural OA. Knee biomechanics were symmetrical in those with bilateral pain and structural OA and in the pain free control group. Conclusions The presence of pain unilaterally appears to be associated with asymmetries in knee biomechanics. Contrary to this, bilateral pain is associated with symmetry. This suggests that the symptomatic status of both knees should be considered when contemplating unilateral or bilateral biomechanical interventions for medial knee OA.

OBJECTIVE: Mediolateral knee movement can be assessed visually with clinical tests. A knee-medial-to-foot position is associated with an increased risk of knee injuries and pathologies. However, the implications of such findings on daily tasks are not well understood. The aim of this study was to investigate if a knee-medial-to-foot position assessed during a clinical test was associated with altered hip and knee joint kinematics and knee joint kinetics during gait compared with those with a knee-over-foot position. DESIGN: Participants were visually assessed during a single-limb mini squat test and classified by a physiotherapist as exhibiting either a knee-medial-to-foot or knee-over-foot position. A comparison of 3-dimensional hip and knee gait kinematics and kinetics between the knee-over-foot and knee-medial-to-foot classifications was performed. SETTING: Research laboratory. PARTICIPANTS: Twenty-five healthy participants were recruited and visually assessed as either knee-over-foot (n = 15; 26.2 ± 6.1 years) or knee-medial-to-foot (n = 10; 24.8 ± 4.1 years). INTERVENTIONS: None. MAIN OUTCOME MEASURES: Peak knee valgus angle and peak internal hip rotation during normal gait. RESULTS: No differences were observed in peak knee valgus angle [3.6 (3.7) vs 5.2 (2.5) degrees; P = 0.19], peak internal hip rotation [8.4 (7.0) vs 4.3 (8.1) degrees; P = 0.21], or knee joint kinetics between groups. CONCLUSIONS: A knee-medial-to-foot position observed during the single-limb mini squat was not reflected during gait measured by 3-dimensional motion analysis in knee healthy individuals. Furthermore, those assessed to have a knee-medial-to-foot position did not display increased loading of the knee joint compared with the knee-over-foot group. Care should be taken when extrapolating results from one movement to another. (Less)

Osteoarthritis (OA) is a common chronic joint condition predominantly affecting the knee, hip, and hand joints. Exercise plays a role in the development and treatment of OA but most of the literature in this area relates to knee OA. While studies indicate that exercise and physical activity have a generally positive effect on healthy cartilage metrics, depending upon the type of the activity and its intensity, the risk of OA development does appear to be moderately increased with sporting participation. In particular, joint injury associated with sports participation may be largely responsible for this increased risk of OA with sport. Various repetitive occupational tasks are also linked to greater likelihood of OA development. There are a number of physical impairments associated with OA including pain, muscle weakness and altered muscle function, reduced proprioception and postural control, joint instability, restricted range of motion, and lower aerobic fitness. These can result directly from the OA pathological process and/or indirectly as a result of factors such as pain, effusion, and reduced activity levels. These impairments and their underlying physiology are often targeted by exercise interventions and evidence generally shows that many of these can be modified by specific exercise. There is currently little clinical trial evidence to show that exercise can alter mechanical load and structural disease progression in those with established OA, although a number of impairments, that are amenable to change with exercise, appears to be associated with increased mechanical load and/or disease progression in longitudinal studies. © 2011 American Physiological Society. Compr Physiol 1:1943-2008, 2011.

Impact loading during walking has been associated with overuse related musculoskeletal disorders, such as osteoarthritis. This study was designed to determine the effect of two shoe insole designs on impact-related loading during walking. In total, 22 healthy adults walked along a 10-m walkway in three different insole conditions: (i) no insole; (ii) flat material insole; (iii) heel-cup insole. Impact forces at the ground were determined and estimated at the knee in a subset of participants (n = 14). Repeated measures ANOVA revealed a significant reduction in peak vertical ground reaction force (vGRF) with the flat material insole compared with the no insole and heel-cup conditions (p = 0.001). No differences between conditions were observed in vGRF loading rate (p > 0.05). Peak impact force at the knee was reduced with flat material insoles and heel-cup insoles (p < 0.05). These data indicate that reductions in impact forces during walking are dependent upon insole design. STATEMENT OF RELEVANCE: This study provides new evidence that impact loads are reduced with shoe insoles during walking. High impact loads are implicated in the development and progression of knee pathologies, including osteoarthritis. Thus, these findings indicate that insole use may be beneficial for various musculoskeletal disorders, including key public health problems such as osteoarthritis.

Hamstring motor behaviour and resultant antagonist torque during knee extension has been quantified in uninjured individuals however, the effect of ACL rupture and ACL reconstruction (ACLR) on the morphology of hamstring antagonist torque generated in vivo is unknown. The purpose of this cross-sectional study was to quantify the hamstring antagonist torque generated in vivo during isokinetic knee extension in ACLD and ACLR patients relative to uninjured control subjects. Ten male ACL deficient (ACLD) subjects (18-35 years), 14 matched males who had undergone ACLR using the bone-patellar tendon-bone graft and 22 matched male control subjects participated. We used a mathematical model to estimate the opposing torque generated by the hamstrings during isokinetic knee extension in 10 degrees intervals from 80 degrees to 10 degrees knee flexion. Control group hamstring antagonist torque was significantly lower at 80-70 degrees knee flexion compared with that of the ACLD (% Diff=40.2; p=0.019) and ACLR (% Diff=34.8; p=0.036) groups. For all subject groups, hamstring antagonist torque demonstrated a descending-ascending curve; decreasing significantly from 80-70 degrees to 50-40 degrees knee flexion (% Diff=40.8 to 63.3; p=0.001 to 0.009) but then increasing significantly from 50-40 degrees to 20-10 degrees knee flexion (% Diff=37.6 to 59.0; p=0.001 to 0.012). ACL status and therefore, the ACL-hamstring reflex has little effect on the magnitude of hamstring antagonist torque generated during quadriceps-induced knee joint loading. Capsular afferents are thought to dictate the hamstring torque profile which decreased then increased during knee extension to maintain dynamic joint stability.

Objective To compare differences in knee varus and valgus angular laxity and passive mechanical stiffness between asymptomatic knees and those with mild, moderate, and severe knee osteoarthritis (OA). Methods A total of 127 participants with symptomatic medial tibiofemoral OA and 32 asymptomatic controls participated. OA knees were stratified according to radiographic severity. Varus–valgus laxity was evaluated using a customized dynamometer, providing continuous measurement of varus–valgus joint angle and torque. The following indices were calculated: 1) varus, valgus, and total angular laxity, 2) end-range varus and valgus stiffness, and 3) midrange stiffness. Results There was no difference in varus, valgus, and total angular laxity, or varus and valgus end-range stiffness between the groups (P > 0.05 for all). The OA groups were less stiff in the midrange compared with the controls (P = 0.004–0.043). Conclusion The absence of differences in total angular laxity is contrary to previous findings, and may be associated with the failure of previous work to account for body size effects. Less midrange stiffness in OA participants compared with controls may indicate less rotational support provided by passive joint structures in knee OA within the functionally important range. The role of passive varus–valgus stiffness in disease onset and progression is worthy of further investigation.

Objective: The purpose of this study was to investigate the relation between knee functionality of anterior cruciate ligament deficient (ACLD) and anterior cruciate ligament reconstruction (ACLR) patients and hamstring antagonist torque generated during resisted knee extension. Design: Cross-sectional. Setting: Laboratory based. Participants: Male ACLD subjects (n=10) (18–35y) and 27 matched males who had undergone ACLR (14 patella tendon [PT] grafts and 13 combined semitendinosus/gracilis tendon grafts). Interventions: Not applicable. Main Outcome Measures: Knee functionality was rated (0- to 100-point scale) by using the Cincinnati Knee Rating System. Using electromyography data from the semitendinosus (ST) and biceps femoris muscles, we created a mathematical model to estimate the opposing torque generated by the hamstrings during isokinetic knee extension in 10° intervals from 80° to 10° knee flexion. Results: Pearson product-moment correlations revealed that more functional ACLD subjects generated significantly (P < .05) higher hamstring antagonist torque throughout knee extension. In contrast, more functional PT subjects produced significantly lower hamstring antagonist torque at 80° to 70° knee flexion, whereas no significant associations were found between hamstring antagonist torque and knee functionality for the ST/gracilis tendon subjects. Conclusions: An increased hamstring antagonist torque generated by the more functional ACLD subjects, reflective of increased hamstring contractile force, is thought to represent a protective mechanism to compensate for mechanical instability. The restoration of anterior knee stability through ACLR negates the need for augmented hamstring antagonist torque.

Purpose: The role of applied external loads in tibial stress fracture is poorly understood. The purpose of this study was to determine whether the magnitude and angle of frontal and sagittal force vectors and the magnitude of the free moment of ground reaction force (the torsional moment between the foot and the ground) during running gait differ between military recruits with and without a history of tibial stress fracture. Methods: Ten male military recruits with tibial stress fracture history and 20 matched controls performed shod running trials over a force plate. The magnitude and the direction of the frontal and sagittal plane ground reaction force, in addition to the free moment, were compared between the groups. Results: The frontal plane force vector was directed significantly more medially in the stress fracture group during midstance and late stance (P < 0.05). The magnitude of frontal and sagittal plane ground reaction forces and the free moment were not higher in the stress fracture group compared with controls. Conclusion: These data highlight differences in the direction with which external forces in the frontal plane are applied in military recruits with a history of tibial stress fracture. These differences may be important in the development of the injury.

A stress fracture represents the inability of the skeleton to withstand repetitive bouts of mechanical loading, which results in structural fatigue, and resultant signs and symptoms of localised pain and tenderness. Reports of stress fractures in female football players are not prevalent; however, they are probably under‐reported and their importance lies in the morbidity that they cause in terms of time lost from participation. By considering risk factors for stress fractures in female football players it may be possible to reduce the impact of these troublesome injuries. Risk factors for stress fractures in female football players include intrinsic risk factors such as gender, endocrine, nutritional, physical fitness and neuromusculoskeletal factors, as well as extrinsic risk factors such as training programme, equipment and environmental factors. This paper discusses these risk factors and their implications in terms of developing prevention and management strategies for stress fractures in female football players.

OBJECTIVE: Patients undergoing arthroscopic partial meniscectomy (APM) are at increased risk of knee osteoarthritis (OA). Meniscal damage and/or surgery may alter knee joint loading to increase OA risk. We investigated changes in knee joint loading following medial APM surgery, compared with the contra-lateral leg.METHODS: We estimated indices of knee joint loading (external peak knee adduction moment (KAM), KAM impulse and peak knee flexion moment (KFM)) normalized to body size (i.e., body mass (BM) and height (HT)) using 3D gait analysis in 23 patients (17 men, mean (SD) 46.2 (6.4) years, BMI 25.8 (3.4) kg/m(2)) without radiographic knee OA before and 12 months after medial APM. Static alignment was assessed by radiography and self-reported outcomes by Knee injury and Osteoarthritis Outcome Score (KOOS).RESULTS: Peak KAM and KAM impulse increased in the APM leg compared to the contra-lateral leg from before to 12 months after surgery (change difference: 0.38 Nm/BM*HT% 95% CI 0.01 to 0.76 (P = 0.049) and 0.20 Nm*s/BM*HT% 95% CI 0.10 to 0.30 (P < 0.001)). Patients self-reported improvements on all KOOS subscales (KOOS pain improvement: 22.8 95% CI 14.5 to 31.0 (P < 0.01)).CONCLUSIONS: A relative increase in indices of medial compartment loading was observed in the leg undergoing APM compared with the contra-lateral leg from before to 12 months after surgery. This increase may contribute to the elevated risk of knee OA in these patients. Randomized trials including a non-surgical control group are needed to determine if changes in joint loading following APM are caused by surgery or by changes in symptoms.

Identification of the impact peak (IP) from the vertical ground reaction force (vGRF) is required to calculate indices of impact loading during running. The IP, however, is not always clearly discernible. Previous researchers have estimated the timing of the IP using surrogate methods, the most common of which is a set time point of 13% stance (TPS). Information contained within the high frequency (HiF) component of the vGRF may also have a utility as a surrogate measure, but the validity of either approach is currently unknown. The purpose of this study is to evaluate the criterion validity for a newly proposed HiF method and the previously used TPS method against a criterion measure for a group of rear-foot striking runners. Fifty participants ran at a standardized speed (3.3 m·s(-1)) on an instrumented treadmill. Five consecutive stance phases were analyzed for the participant's dominant limb. Bland-Altman was used to assess agreement between the criterion method and each surrogate method. Good agreement of the HiF and TPS methods with the criterion method indicate that both methods are likely to be valid surrogate approaches to estimate vGRF impact loading indices. For all impact loading indices, smaller bias and limits of agreement (LOA) were observed with the HiF method when compared to the TPS method. Therefore, it is concluded that the HiF method should be used in preference to the TPS method when it is available.

Background Patients following meniscectomy are at increased risk of developing knee osteoarthritis in the tibiofemoral compartment and at the patellofemoral joint. As osteoarthritis is widely considered a mechanical disease, it is important to understand the potential effect of arthroscopic partial meniscectomy (APM) on knee joint mechanics. The purpose of this study was to evaluate changes in knee joint biomechanics during a forward lunge in patients with a suspected degenerative meniscal tear from before to three months after APM. Methods Twenty-two patients (35–55 years old) with a suspected degenerative medial meniscal tear participated in this study. Three dimensional knee biomechanics were assessed on the injured and contralateral leg before and three months after APM. The visual analogue scale was used to assess knee pain and the Knee Injury Osteoarthritis Outcome Score was used to assess sport/recreation function and knee-related confidence before and after APM. Results The external peak knee flexion moment reduced in the APM leg compared to the contralateral leg (mean difference (95% CI)) − 1.08 (− 1.80 to − 0.35) (Nm/(BW × HT)%), p = 0.004. Peak knee flexion angle also reduced in the APM leg compared to the contralateral leg − 3.94 (− 6.27 to − 1.60) degrees, p = 0.001. There was no change in knee pain between the APM leg and contralateral leg (p = 0.118). Self-reported sport/recreation function improved (p = 0.004). Conclusions Although patients self-reported less difficulty during strenuous tasks following APM, patients used less knee flexion, a strategy that may limit excessive patellar loads during forward lunge in the recently operated leg.

Background Exercise related leg pain (ERLP) is a common lower limb overuse injury characterised by pain located between the knee and ankle that occurs during activity. The high incidence of the condition, subsequent interference with participation in physical activity and substantial recovery time, highlights a need for effective interventions. Whilst many interventions have been described for the management of ERLP, currently there is a lack of high quality evidence for an effective intervention for the condition. Methods/Design A single-blinded randomised controlled clinical trial will be conducted in a community setting. Forty-five female volunteers aged between 18 and 40 years with a history of insidious onset of pain located between the knee and ankle of at least one month duration that is aggravated by weight bearing activities will be recruited for the study. Suitable participants will be randomly allocated to one of three treatment groups for the 6 week intervention period: (i) exercise only, (ii) rigid anti-pronation tape and exercise, (iii) elastic anti-pronation tape and exercise. Outcomes will be measured at baseline, 1, 2 and 6 weeks using primary outcome measures of usual and worst pain visual analogue scale and global perceived improvement. Secondary outcome measures will include Foot and Ankle Ability Measure, Patient Specific Functional Scale and amount of activity in the previous week. In addition, participants will be contacted by phone to obtain primary and secondary outcome measures at 12, 18, 24 and 30 weeks. Discussion This article describes a single-blinded randomised controlled clinical trial that will utilise high quality methodologies in accordance with CONSORT guidelines. The results of this study will contribute to the limited knowledge regarding effective interventions for the management of ERLP. Trial registration Australian New Zealand Clinical Trials Registry (ACTRN12613000914763) Electronic supplementary material The online version of this article (doi:10.1186/1471-2474-15-328) contains supplementary material, which is available to authorized users.

OBJECTIVE: We performed a systematic review, meta-analysis and assessed the evidence supporting a causal link between knee joint loading during walking and structural knee osteoarthritis (OA) progression.DESIGN: Systematic review, meta-analysis and application of Bradford Hill's considerations on causation.DATA SOURCES: We searched MEDLINE, Scopus, AMED, CINAHL and SportsDiscus for prospective cohort studies and randomised controlled trials (RCTs) from 1950 through October 2013.STUDY ELIGIBILITY CRITERIA: We selected cohort studies and RCTs in which estimates of knee joint loading during walking were used to predict structural knee OA progression assessed by X-ray or MRI.DATA ANALYSES: Meta-analysis was performed to estimate the combined OR for structural disease progression with higher baseline loading. The likelihood of a causal link between knee joint loading and OA progression was assessed from cohort studies using the Bradford Hill guidelines to derive a 0-4 causation score based on four criteria and examined for confirmation in RCTs.RESULTS: Of the 1078 potentially eligible articles, 5 prospective cohort studies were included. The studies included a total of 452 patients relating joint loading to disease progression over 12-72 months. There were very serious limitations associated with the methodological quality of the included studies. The combined OR for disease progression was 1.90 (95% CI 0.85 to 4.25; I(2)=77%) for each one-unit increment in baseline knee loading. The combined causation score was 0, indicating no causal association between knee loading and knee OA progression. No RCTs were found to confirm or refute the findings from the cohort studies.CONCLUSIONS: There is very limited and low-quality evidence to support for a causal link between knee joint loading during walking and structural progression of knee OA.TRIAL REGISTRATION NUMBER: CRD42012003253.

Background: Passive mechanical behavior of the knee in the frontal plane, measured as angular laxity and mechanical stiffness, may play an important role in the pathogenesis of knee osteoarthritis (OA). Little is known about knee laxity and stiffness prior to knee OA onset. We investigated knee joint angular laxity and passive stiffness in meniscectomized patients at high risk of knee OA compared with healthy controls. Methods: Sixty patients meniscectomized for a medial meniscal tear (52 men, 41.4 ± 5.5. years, 175.3 ± 7.9. cm, 83.6 ± 12.8. kg, mean ± SD) and 21 healthy controls (18 men, 42.0 ± 6.7. years, 176.8 ± 5.7. cm, 77.8 ± 13.4. kg) had their knee joint angular laxity and passive stiffness assessed twice ~. 2.3. years apart. Linear regression models including age, sex, height and body mass as covariates in the adjusted model were used to assess differences between groups. Results: Greater knee joint varus (- 10.1 vs. - 7.3°, p < 0.001), valgus (7.1 vs. 5.6°, p = 0.001) and total (17.2 vs. 12.9°, p < 0.001) angular laxity together with reduced midrange passive stiffness (1.71 vs. 2.36. Nm/°, p < 0.001) were observed in patients vs. healthy controls. No differences were observed in change in stiffness over time between patients and controls, however a tendency towards increased laxity in patients was seen. Conclusions: Meniscectomized patients showed increased knee joint angular laxity and reduced passive stiffness ~. 3. months post surgery compared with controls. In addition, the results indicated that knee joint laxity may increase over time in meniscectomized patients.

SummaryObjectiveTo evaluate the relationship between dynamic mechanical loading, as indicated by external knee adduction moment (KAM) measures during walking, and measures of articular cartilage morphology and subchondral bone size in people with medial knee osteoarthritis (OA).Design180 individuals with radiographic medial tibiofemoral OA participated. Peak KAM and KAM angular impulse were measured by walking gait analysis. Tibial cartilage volume and plateau bone area, and tibiofemoral cartilage defects were determined from magnetic resonance imaging using validated methods.ResultsBoth peak KAM (coefficient=0.42, 95% confidence interval (CI) 0.04–0.79, P=0.03) and KAM impulse (coefficient=1.79, 95% CI 0.80–2.78, P