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Patellofemoral joint (PFJ) osteoarthritis is common following anterior cruciate ligament reconstruction (ACLR) and may be linked with altered joint loading. However, little is known about the cross‐sectional and longitudinal relationship between PFJ loading and osteoarthritis post‐ACLR. This study tested if altered PFJ loading is associated with prevalent and worsening early PFJ osteoarthritis post‐ACLR. Forty‐six participants (mean ± 1 SD age 26 ± 5 years) approximately 1‐year post‐ACLR underwent magnetic resonance imaging (MRI) and biomechanical assessment of their reconstructed knee. Trunk and lower‐limb kinematics plus ground reaction forces were recorded during the landing phase of a standardized forward hop. These data were input into a musculoskeletal model to calculate the PFJ contact force. Follow‐up MRI was completed on 32 participants at 5‐years post‐ACLR. Generalized linear models (Poisson regression) assessed the relationship between PFJ loading and prevalent early PFJ osteoarthritis (i.e., presence of a PFJ cartilage lesion at 1‐year post‐ACLR) and worsening PFJ osteoarthritis (i.e., incident/progressive PFJ cartilage lesion between 1‐ and 5‐years post‐ACLR). A lower peak PFJ contact force was associated with prevalent early PFJ osteoarthritis at 1‐year post‐ACLR (n = 14 [30.4%]; prevalence ratio: 1.37; 95% confidence interval [CI]: 1.02–1.85) and a higher risk of worsening PFJ osteoarthritis between 1‐ and 5‐years post‐ACLR (n = 9 [28.1%]; risk ratio: 1.55, 95% CI: 1.13–2.11). Young adults post‐ACLR who exhibited lower PFJ loading during hopping were more likely to have early PFJ osteoarthritis at 1‐year and worsening PFJ osteoarthritis between 1‐ and 5‐years. Clinical interventions aimed at mitigating osteoarthritis progression may be beneficial for those with signs of lower PFJ loading post‐ACLR. [ABSTRACT FROM AUTHOR]

Background: Patellofemoral pain is highly prevalent across the lifespan, and a significant proportion of people report unfavourable outcomes years after diagnosis. Previous research has implicated patellofemoral joint loading during gait in patellofemoral pain and its sequelae, patellofemoral osteoarthritis. Biomechanical foot-based interventions (e.g., footwear, insoles, orthotics, taping or bracing) can alter patellofemoral joint loads by reducing motions at the foot that increase compression between the patella and underlying femur via coupling mechanisms, making them a promising treatment option. This systematic review will summarise the evidence about the effect of biomechanical foot-based interventions on patellofemoral joint loads during gait in adults with and without patellofemoral pain and osteoarthritis. Methods: MEDLINE (Ovid), the Cumulative Index to Nursing and Allied Health Literature CINAHL, The Cochrane Central Register of Controlled Trials (CENTRAL), SPORTdiscus (EBSCO) and Embase (Ovid) will be searched. Our search strategy will include terms related to 'patellofemoral joint', 'loads' and 'biomechanical foot-based interventions'. We will include studies published in the English language that assess the effect of biomechanical foot-based interventions on patellofemoral joint loads, quantified by patellofemoral joint pressure, patellofemoral joint reaction force and/or knee flexion moment. Two reviewers will independently screen titles and abstracts, complete full-text reviews, and extract data from included studies. Two reviewers will assess study quality using the Revised Cochrane Risk of Bias (RoB 2) tool or the Cochrane Risk Of Bias In Non-Randomized Studies – of Interventions (ROBINS-I) tool. We will provide a synthesis of the included studies' characteristics and results. If three or more studies are sufficiently similar in population and intervention, we will pool the data to conduct a meta-analysis and report findings as standardised mean differences with 95% confidence intervals. If a meta-analysis cannot be performed, we will conduct a narrative synthesis of the results and produce forest plots for individual studies. Discussion: This protocol outlines the methods of a systematic review that will determine the effect of biomechanical foot-based interventions on patellofemoral joint loads. Our findings will inform clinical practice by identifying biomechanical foot-based interventions that reduce or increase patellofemoral joint loads, which may aid the treatment of adults with patellofemoral pain and osteoarthritis. Trial registration: Registered with PROSPERO on the 4th of May 2022 (CRD42022315207). [ABSTRACT FROM AUTHOR]

Altered biomechanics are frequently observed following anterior cruciate ligament reconstruction (ACLR). Yet, little is known about knee‐joint loading, particularly in the patellofemoral‐joint, despite patellofemoral‐joint osteoarthritis commonly occurring post‐ACLR. This study compared knee‐joint reaction forces and impulses during the landing phase of a single‐leg forward hop in the reconstructed knee of people 12‐24 months post‐ACLR and uninjured controls. Experimental marker data and ground forces for 66 participants with ACLR (28 ± 6 years, 78 ± 15 kg) and 33 uninjured controls (26 ± 5 years, 70 ± 12 kg) were input into scaled‐generic musculoskeletal models to calculate joint angles, joint moments, muscle forces, and the knee‐joint reaction forces and impulses. The ACLR group exhibited a lower peak knee flexion angle (mean difference: −6°; 95% confidence interval: [−10°, −2°]), internal knee extension moment (−3.63 [−5.29, −1.97] percentage of body weight × participant height (body weight [BW] × HT), external knee adduction moment (‐1.36 [−2.16, −0.56]% BW × HT) and quadriceps force (−2.02 [−2.95, −1.09] BW). The ACLR group also exhibited a lower peak patellofemoral‐joint compressive force (−2.24 [−3.31, −1.18] BW), net tibiofemoral‐joint compressive force (−0.74 [−1.20, 0.28] BW), and medial compartment force (−0.76 [−1.08, −0.44] BW). Finally, only the impulse of the patellofemoral‐joint compressive force was lower in the ACLR group (−0.13 [−0.23, −0.03] body weight‐seconds). Lower compressive forces are evident in the patellofemoral‐ and tibiofemoral‐joints of ACLR knees compared to uninjured controls during a single‐leg forward hop‐landing task. Our findings may have implications for understanding the contributing factors for incidence and progression of knee osteoarthritis after ACLR surgery. [ABSTRACT FROM AUTHOR]

ABSTRACT: Cartilage T2 relaxation time in isolated anterior cruciate ligament reconstruction (ACLR) without concomitant meniscal pathology and their changes over time remain unclear. The purpose of this exploratory study was to: (i) compare cartilage T2 relaxation time (T2 values) in people with isolated ACLR at 2–3 years post‐surgery (baseline) and matched healthy controls and; (ii) evaluate the subsequent 2‐year change in T2 values in people with ACLR. Twenty‐eight participants with isolated ACLR and nine healthy volunteers underwent knee magnetic resonance imaging (MRI) at baseline; 16 ACLR participants were re‐imaged 2 years later. Cartilage T2 values in full thickness, superficial layers, and deep layers were quantified in the tibia, femur, trochlear, and patella. Between‐group comparisons at baseline were performed using analysis of covariance adjusting for age, sex, and body mass index. Changes over time in the ACLR group were evaluated using paired sample t‐tests. ACLR participants showed significantly higher (p = 0.03) T2 values in the deep layer of medial femoral condyle at baseline compared to controls (mean difference 4.4 ms [13%], 95%CI 0.4, 8.3 ms). Over 2 years, ACLR participants showed a significant reduction (p = 0.04) in T2 value in the deep layer of lateral tibia (mean change 1.4 ms [−7%], 95%CI 0.04, 2.8 ms). The decrease in T2 values suggests improvement in cartilage composition in the lateral tibia (deep layer) of ACLR participants. Further research with larger ACLR cohorts divided according to meniscal status and matched healthy cohorts are needed to further understand cartilage changes post‐ACLR. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2022–2029, 2018. [ABSTRACT FROM AUTHOR]

Background Although various methods for quantifying outcomes following total knee replacement ( TKR) are used, there are few studies of the relationships between patient reported scores and functional tests. This paper aims to assess the relationships between commonly used outcome scores after TKR through a prospective cohort study. Methods Twenty-four patients who had undergone unilateral TKR were assessed using four patient-reported outcome scores as well as objective measurements of knee laxity, quadriceps muscle strength and the Timed Up and Go Test. All scores and measures were correlated using the Pearson product moment correlation coefficient using the lower one-sided 95% confidence interval. A level of significance of P < 0.05 was selected. Results The Timed Up and Go Test was the only objective measure to demonstrate a statistically significant correlation ( r = −0.557 to −0.770, P = 0.0001-0.005) with patient-reported scores. Conclusion A comprehensive assessment of outcomes after TKR requires both subjective and objective assessments. Walking ability and speed are important to the TKR patient and are representative of their pain and function. [ABSTRACT FROM AUTHOR]

ABSTRACT Hindfoot arthritis is an important contributor to foot pain and physical disability. While the subtalar joint (STJ) is most frequently affected, anatomical variants such as facet configuration were suggested to further STJ cartilage deterioration. T2* mapping enables detection of ultra-structural cartilage change, particularly in thin cartilage layers, but its feasibility in the STJ has not yet been evaluated. The purpose of this study was to evaluate segmentation consistency and inter-scan short-term precision error of T2* mapping of talocalcaneal cartilage and to investigate the relationship between facet configuration and STJ T2* values. Using 3Tesla morphological magnetic resonance imaging, STJ configuration was categorized according to the degree of fusion between anterior, medial, or posterior facets. Subsequently, two repeats of multi-echo gradient recalled echo sequences were performed to obtain T2* maps with repositioning. Segmentation consistency of T2* values attained an ICC of 0.90 (95%CI 0.69-0.99). Precision errors comprised a coefficient of variation (CV) ranging 0.01-0.05, corresponding to a root mean square CV of 0.03-0.04. A 2-joint configuration type (i.e., fused anterior-medial facets) was significantly associated with a decrease in posterior facet T2* values ( β = −0.6, p = 0.046). STJ T2* mapping is a reliable method requiring at least a 4% difference within people to enable detection of significant change. Anatomical variants in STJ configuration were associated with T2* values with the more stable 3-joint types exhibiting more favorable cartilage outcomes. Longer-term larger-scaled studies focusing on arthritis pathology are needed to further support the use of T2* mapping in hindfoot disease monitoring. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1969-1976, 2016. [ABSTRACT FROM AUTHOR]

Objective: To evaluate single-leg squat performance 1-2 years after arthroscopy for intra-articular hip pathology compared with control subjects and the nonsurgical limb, and to investigate whether single-leg squat performance on the operated limb was associated with hip muscle strength.Design: Cross-sectional study.Setting: Private physiotherapy clinic and university laboratory.Participants: Thirty-four participants (17 women, 36.7 ± 12.6 years) 1-2 years after hip arthroscopy and 34 gender-matched control subjects (17 women, 33.1 ± 11.9 years).Methods: Participants performed single-leg squats using a standardized testing procedure. Squat performance was captured using video. Video footage was uploaded and reformatted for analyses. Hip muscle strength was measured with handheld dynamometry using reliable methods.Outcome Measures: Frontal plane pelvic obliquity, hip adduction, and knee valgus were measured. Repeated measures analysis of variance evaluated between-group differences, with limb as a within-subjects factor (surgical versus nonsurgical) and gender as a between-subjects factor (P < .05).Results: The hip arthroscopy group demonstrated significantly greater apparent hip adduction (mean difference 2.7°, 95% confidence interval [CI] 0.7°-4.8°) and apparent knee valgus (4.0°, 95% CI 1.0°-7.1°) at peak squat depth compared with control subjects. The operated limb also demonstrated significantly greater pelvic obliquity during single-leg stance compared with the nonsurgical limb (1.2°, 95% CI 0.1°-2.3°). Women had significantly greater apparent hip adduction (standing 1.6°, 95% CI 0.5°-2.6°; peak squat depth 2.4°, 95% CI 0.3°-4.4°) and apparent knee valgus (standing 3.3°, 95% CI 1.8°-4.7°; peak squat depth 3.1°, 95% CI 0°-6.1°). Significant positive correlations were found between frontal plane angles and hip flexor and extensor peak torque (P > .05).Conclusion: One to 2 years after hip arthroscopy, deficits in single-leg squat performance exist that have the potential to increase hip joint impingement and perpetuate postoperative symptoms. Rehabilitation after hip arthroscopy should target retraining in functional single-leg positions. [ABSTRACT FROM AUTHOR]

ABSTRACT In addition to biomechanical disturbances, peripheral joint injuries (PJIs) can also result in chronic neuromuscular alterations due in part to loss of mechanoreceptor-mediated afferent feedback. An emerging perspective is that PJI should be viewed as a neurophysiological dysfunction, not simply a local injury. Neurophysiological and neuroimaging studies have provided some evidence for central nervous system (CNS) reorganization at both the cortical and spinal levels after PJI. The novel hypothesis proposed is that CNS reorganization is the underlying mechanism for persisting neuromuscular deficits after injury, particularly muscle weakness. There is a lack of direct evidence to support this hypothesis, but future studies utilizing force-matching tasks with superimposed transcranial magnetic stimulation may be help clarify this notion. Muscle Nerve 51: 327-332, 2015 [ABSTRACT FROM AUTHOR]

Background: The evaluation of foot posture in a clinical setting is useful to screen for potential injury, however disagreement remains as to which method has the greatest clinical utility. An inexpensive and widely available imaging system, the Microsoft Kinect™, may possess the characteristics to objectively evaluate static foot posture in a clinical setting with high accuracy. The aim of this study was to assess the intra-rater reliability and validity of this system for assessing static foot posture. Methods: Three measures were used to assess static foot posture; traditional visual observation using the Foot Posture Index (FPI), a 3D motion analysis (3DMA) system and software designed to collect and analyse image and depth data from the Kinect. Spearman's rho was used to assess intra-rater reliability and concurrent validity of the Kinect to evaluate foot posture, and a linear regression was used to examine the ability of the Kinect to predict total visual FPI score. Results: The Kinect demonstrated moderate to good intra-rater reliability for four FPI items of foot posture (? = 0.62 to 0.78) and moderate to good correlations with the 3DMA system for four items of foot posture (? = 0.51 to 0.85). In contrast, intra-rater reliability of visual FPI items was poor to moderate (? = 0.17 to 0.63), and correlations with the Kinect and 3DMA systems were poor (absolute ? = 0.01 to 0.44). Kinect FPI items with moderate to good reliability predicted 61% of the variance in total visual FPI score. Conclusions: The majority of the foot posture items derived using the Kinect were more reliable than the traditional visual assessment of FPI, and were valid when compared to a 3DMA system. Individual foot posture items recorded using the Kinect were also shown to predict a moderate degree of variance in the total visual FPI score. Combined, these results support the future potential of the Kinect to accurately evaluate static foot posture in a clinical setting. [ABSTRACT FROM AUTHOR]

Objective Knee extensor strength is an important correlate of physical function in patients with knee osteoarthritis; however, it remains unclear whether standing balance is also a correlate. The purpose of this study was to evaluate the cross-sectional associations of knee extensor strength, standing balance, and their interaction with physical function. Methods One hundred four older adults with end-stage knee osteoarthritis awaiting a total knee replacement (mean ± SD age 67 ± 8 years) participated. Isometric knee extensor strength was measured using an isokinetic dynamometer. Standing balance performance was measured by the center of pressure displacement during quiet standing on a balance board. Physical function was measured by the self-report Short Form 36 (SF-36) questionnaire and by the 10-meter fast-pace gait speed test. Results After adjustment for demographic and knee pain variables, we detected significant knee strength by standing balance interaction terms for both SF-36 physical function and fast-pace gait speed. Interrogation of the interaction revealed that standing balance in the anteroposterior plane was positively related to physical function among patients with lower knee extensor strength. Conversely, among patients with higher knee extensor strength, the standing balance-physical function associations were, or tended to be, negative. Conclusion These findings suggest that although standing balance was related to physical function in patients with knee osteoarthritis, this relationship was complex and dependent on knee extensor strength level. These results are of importance in developing intervention strategies and refining theoretical models, but they call for further study. [ABSTRACT FROM AUTHOR]

The purposes of this study were (i) to examine the effects of anterior cruciate ligament (ACL) status on hamstring force steadiness, peak hamstring strength, quadriceps (antagonist) activation, and physical performance, and (ii) to evaluate the associations of physical performance with hamstring steadiness and hamstring strength. Thirteen subjects with unilateral deficiency of the ACL (ACLD), 39 matched subjects with unilateral reconstructed ACL (ACLR; n = 25 with bone-patella tendon-bone (ACLR-PT) graft and n = 14 with combined semitendinosus and gracilis tendon (ACLR-STGT) graft) and 33 control subjects participated. Each subject performed maximal-effort isokinetic knee flexion repetitions at 180° s with electromyography (EMG) electrodes attached to their medial and lateral quadriceps muscles. Physical performance was assessed using the single-limb long hop for distance. Wavelet-derived mean instantaneous frequency (Mi f) of flexor torque-time curves was significantly ( p < 0.05) higher (i.e., less smooth) in ACLR-STGT subjects compared to the ACLD, ACLR-PT and control subjects. No significant differences existed for peak hamstrings strength (i.e., peak torque produced) or quadriceps antagonist EMG activity. Positive correlations were identified between hamstrings force steadiness and quadriceps antagonist activity for ACLD ( r = 0.797), ACLR-PT ( r = 0.467), and ACLR-STGT ( r = 0.628) subjects. For ACLR-STGT subjects, reduced hamstrings force steadiness associated with poorer long-hop performance ( r = −0.695). Reduced steadiness amongst ACLR-STGT subjects may reflect motor output variability of the antagonist (i.e., quadriceps dyskinesia) and/or agonist musculature-a maladaptive feature which potentially contributes to poorer single-limb hop performance. Measures of hamstring force steadiness in combination with traditional measures of peak hamstring strength provide valuable clinical information regarding knee joint function following ACL injury/ACLR. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:907-914 [ABSTRACT FROM AUTHOR]

The objective of this research was to examine the dynamic restraint mechanism by establishing the neuromuscular characteristics of lower extremity muscles in anterior cruciate ligament reconstruction (ACLR) subjects. This study also investigated neuromuscular variables that relate to post-ACLR functional outcome. Thirteen patients having undergone ACLR using the bone patella tendon bone graft at least 6 months prior participated in this study. Knee functionality (0- to 100-point scale) was rated using the Cincinnati Knee Rating System. The median frequency of the electromyographic (EMG) recordings from the vastus medialis (VM) and vastus lateralis (VL) muscles together with the isokinetic quadriceps torque generated in 10° intervals between 80° and 10° knee flexion was determined for the noninvolved and involved limbs. Lower limb musculotendinous stiffness was also assessed for the noninvolved and involved limbs. Limb symmetry indexes were calculated for each of the physiological measures. Compared to the noninvolved limb, the median frequency of the EMG from the involved limb VM and VL muscles was significantly lower as was the quadriceps torque generated at the seven knee flexion intervals. In contrast, musculotendinous stiffness was significantly higher in the involved lower limb compared to the noninvolved limb. Significant, moderate correlations were identified between knee functionality and symmetry indexes for all variables except for the isokinetic quadriceps torque produced between 80°-70° and 20°-10° knee flexion. More functional ACLR subjects demonstrated enhanced motor unit recruitment reflective of less quadriceps muscle fiber atrophy together with increased quadriceps strength and musculotendinous stiffness of the lower limb musculature. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:126-135, 2008 [ABSTRACT FROM AUTHOR]

Background: Higher peak external knee flexion moments (KFM) during running has been observed in healthy people wearing athletic footwear compared to barefoot, which may increase risk of knee pathologies such as patellofemoral pain. Currently, no studies have examined whether stability and neutral style athletic shoes influence the peak KFM differently, or explored the underlying biomechanical mechanisms by which footwear alters peak KFM in young females. Methods: Lower limb biomechanics of sixty girls aged between 10 and 25 years old were collected while running in footwear (both stability and neutral) and barefoot. The external peak KFM, sagittal plane kinematics, sagittal plane knee ground reaction force (GRF) lever arm and sagittal plane resultant GRF magnitude were analysed by repeated measures Analysis of Variance. Linear mixed models were fit to identify predictors of a change in peak KFM, and to determine if the effects of these predictors differed between footwear conditions. Results: The peak KFM was higher wearing both shoe styles compared to barefoot (p < 0.001), while no between-shoe differences were found (p > 0.05). Both shoes also increased kinematic variables at the hip, knee, and ankle (p < 0.05). When all these variables were entered into the mixed model, only a change in the knee-GRF lever arm was predictive of a change in peak KFM wearing shoes compared to barefoot (p < 0.001). Conclusion: These findings provide evidence that stability and neutral shoes increase peak KFM compared to barefoot, which is associated with a change in the knee-GRF lever arm rather than a change in lower limb kinematics. Future studies may consider manipulating footwear characteristics to reduce the knee-GRF lever arm in an effort to reduce peak KFM and the potential risk of patellofemoral pain. [ABSTRACT FROM AUTHOR]

Background: Higher landing-related external knee joint moments at later stages of female pubertal development likely contribute to a higher incidence of non-contact anterior cruciate ligament (ACL) injury. Athletic footwear may provide a potential strategy to alter higher knee moments. Methods: Thirty-one late/post-pubertal girls (Tanner stage IV-V, menarche and growth spurt attained) performed a single limb drop lateral jump in three footwear conditions (barefoot, low support shoes and high support shoes), in which peak knee abduction moment (KAbM), flexion moment (KFM) and internal rotation moments (KIRM) were measured. Repeated measures ANOVA and ANCOVA were used to test for a main effect of footwear with and without foot posture index (FPI) as a covariate (p < 0.05) with post-hoc test carried out via Fisher’s Least Significant Difference (LSD). Results: A main effect of footwear condition was observed for peak KFM (p < 0.05), but not KAbM or KIRM, in both unadjusted and adjusted models. Post-hoc analysis demonstrated that both high- and low-support shoes increased peak KFM compared with barefoot (p < 0.001). Conclusion: Our findings indicate commercially available high- and low-supportive footwear increase peak KFM, but do not effect KAbM or KIRM while landing among late/post-pubertal girls. This suggests that these styles of footwear are inadequate at reducing higher knee moments in an at-risk cohort. [ABSTRACT FROM AUTHOR]