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Objective: To explore mechanisms of mechanoinflammation, we investigated the association between the presence of knee synovial perivascular edema and gait biomechanics that serve as surrogate measures of knee load in patients with knee osteoarthritis (OA)., Design: Patients with symptomatic, radiographic knee OA and neutral to varus alignment undergoing total knee arthroplasty or high tibial osteotomy participated in this cross-sectional analysis. All participants underwent 3D gait analysis prior to surgery. Synovial biopsies were obtained during surgery for histopathological assessment. The association between the presence of synovial perivascular edema (predictor) and the external knee moment (outcome) in each orthogonal plane was analyzed using multivariate linear regression and polynomial mixed effects regression models, while adjusting for age, sex, BMI, and gait speed., Results: Ninety-two patients with complete gait and histopathological data were included. When fitted over 100% of stance, regression models indicated substantial differences between patients with and without synovial perivascular edema for knee moments in frontal, sagittal and transverse planes. The knee adduction moment was higher in patients with edema from 16 to 74% of stance, with the largest difference at 33% of stance (β = 6.87 Nm [95%CI 3.02, 10.72]); whereas the knee flexion-extension moment differed from 15 to 92% of stance, with the largest difference in extension at 60% of stance (β = -10.80 Nm [95%CI -16.20, -5.40])., Conclusions: In patients with knee OA, the presence of synovial perivascular edema identified by histopathology is associated with aberrant patterns of knee loading throughout stance, supporting the link between biomechanics and synovial inflammation., (Copyright © 2021 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Objective: Although mechanically-induced inflammation is an appealing explanation linking different etiologic factors in osteoarthritis (OA), clinical research investigating changes in both biomechanics and joint inflammation is limited. The purpose of this study was to evaluate the association between change in surrogate measures of knee load and knee effusion-synovitis in patients with medial compartment knee OA undergoing high tibial osteotomy (HTO)., Methods: Thirty-six patients with medial compartment knee OA and varus alignment underwent 3D gait analysis and 3T magnetic resonance imaging (MRI) preoperatively and 1 year after medial opening wedge HTO. Primary outcome measures were the change in the external knee adduction moment impulse during walking and change in knee suprapatellar effusion-synovitis volume manually segmented on MRI by one blinded assessor., Results: Mean (SD) knee adduction moment impulse [24.0 (6.5) Nm•s] and knee effusion-synovitis volume [8976.7 (8016.9) mm 3 ] suggested substantial preoperative medial knee load and inflammation. 1-year postoperative changes in knee adduction moment impulse [-10.1 Nm•s (95%CI: -12.7, -7.4)], and knee effusion-synovitis volume [-1856 mm 3 (95%CI: -3830, 117)] were positively correlated [r = 0.60 (95% CI 0.34, 0.78)]. Simple linear regression suggested a 448 mm 3 (95%CI: 241, 656) reduction in knee effusion-synovitis volume per 1 Nm•s reduction in knee adduction moment impulse. Change in knee adduction moment impulse explained 36% (R 2  = 0.36) of the variance of change in knee effusion-synovitis volume., Conclusions: Reduction in medial knee load is positively associated with reduction in knee inflammation after HTO, suggesting the phenomenon of mechano-inflammation in patients with knee OA., (Copyright © 2020 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Background: Exercise programs rely on the overload principle, yet patients with knee osteoarthritis (OA) may not adequately progress exercises due to fear of exacerbating symptoms., Objective: To describe trajectories for perceived exertion and exercise-induced knee pain during a neuromuscular exercise program for patients with knee OA., Design: Participants with knee OA completed a 12-week neuromuscular exercise program consisting of weekly supervised sessions plus home exercises. During each supervised session, the Borg's rating of perceived exertion (RPE; 6 = no exertion, 20 = maximal exertion) and knee pain (pre, post, max) using Numeric Rating Scales (NRS; 0 = no pain, 10 = worst imaginable pain) were completed. Mean changes in RPE and pain from weeks 1-12 were calculated. Mixed effects regression was used to investigate trajectories over time (weeks) for RPE, and maximum pain (pre-to-max) and pain-change (pre-to-post) during exercise., Results: 56 patients (95%) completed the program. From week 1-12, RPE increased by 2.6 (95%CI, 1.7 to 3.5), from 'somewhat hard' to 'very hard', while max pain decreased by 1.0 NRS (95%CI, 0.5 to 1.3) and pain-change decreased by 0.9 NRS (95%CI, 0.4 to 1.3). Linear mixed effects regression showed a quadratic increase for RPE over time until between weeks 9 and 10, then RPE plateaued. Maximum pain decreased linearly over time. Pain-change showed a quadratic decrease over time until approximately week 9, then pain-change plateaued., Conclusions: In patients with knee OA participating in a 12-week neuromuscular exercise program, perceived exertion during exercise progressed from 'somewhat hard' to 'very hard' at 9 weeks, while exercise-induced knee pain decreased. Patients were able to work harder while experiencing decreases rather than increases in pain., (Copyright © 2020 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Objectives: Despite the recognized importance of neuromuscular exercises, there is currently no widely accepted clinical outcome measure focused on neuromuscular control for patients with knee osteoarthritis (OA). The purposes of the present study were to investigate the test-retest reliability, concurrent validity and longitudinal validity of the star excursion balance test (SEBT) in patients with knee OA., Design: 74 patients performed the SEBT on two sessions within 7 days, and on a third session after completing 12 weeks of a home exercise program focused on neuromuscular control. A subgroup of 37 performed the SEBT while in the field of view of a motion capture system to estimate concurrent validity. The SEBT was recorded in cm and also normalized to leg length (LL). Participants also completed the 40 m fast-paced walk test and patient-reported outcomes before and after the exercise program., Results: Intraclass correlation coefficients (95% confidence intervals) were 0.94 (0.91 to 0.96) and 0.93 (0.89 to 0.96) and standard errors of measurement were ±2.68 cm and ±3.05%LL for raw and normalized composite scores, respectively. The minimum detectable change at the 95% confidence level for the composite score was 7.44 cm and 8.45%LL. Correlations between observer and motion capture measures were very high (Pearson r > 0.96). There was a significant increase in SEBT following the exercise program (standardized response mean = 0.74). The change in SEBT had low correlations with changes in 40 m walk times (r = 0.26) and pain (r = 0.28)., Conclusion: The SEBT has suitable measurement properties for use in patients with knee OA., (Copyright © 2019 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Objective: To evaluate 5-year outcomes after lower limb realignment and test the hypothesis that surgery-induced changes in selected biomechanical risk factors for medial knee osteoarthritis (OA) are associated with clinically important improvements., Design: We prospectively evaluated patient-reported outcomes, full-limb standing radiographs and gait biomechanics before, 6 months (surgery-induced change) and 5 years after medial opening wedge high tibial osteotomy (HTO) in 170 patients (46.4 ± 8.9 years, 135 males) with knee OA and varus alignment. Logistic regression tested the associations of 6-month changes in mechanical axis angle and knee adduction moment with achieving an increase of ≥10 points in the Knee injury and Osteoarthritis Outcome Score (KOOS)4 at 5 years, with and without adjusting for covariates. Gait data were also compared to existing data from healthy controls., Results: Mean 5-year changes (95% confidence interval (CI)) were: KOOS4: +14.2 (10.8, 17.6); mechanical axis angle: +8.21° (7.58, 8.83); knee adduction moment: -1.49 %BW*Ht (-1.35, -1.63). The postoperative knee adduction moments were typically lower than values for healthy controls. When divided into quartiles, although all strata improved significantly, patients with reductions in knee adduction moment of 1.14-1.74 %BW*Ht (neither largest nor smallest changes) had highest 5-year KOOS4 scores. The 6-month change in knee adduction moment (odds ratios (OR) = 0.38; 95% CI: 0.22, 0.67), preoperative KOOS4 (OR = 0.96; 95% CI: 0.94, 0.99) and preoperative medial tibiofemoral narrowing grade (OR = 0.62; 95% CI: 0.37, 1.00) were negatively associated with having a 5-year clinically important improvement (C-statistic = 0.70)., Conclusions: Substantial improvements in biomechanical risk factors and patient-reported outcomes are observed 5 years after medial opening wedge HTO. The surgery-induced change in load distribution during walking is significantly associated with long-term clinically important improvement., (Copyright © 2017 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

The purpose of this review was to highlight recent research in mechanics and osteoarthritis (OA) by summarizing results from selected studies spanning basic and clinical research methods. Databases were searched from January 2013 through to March 2014. Working in pairs, reviewers selected 67 studies categorized into four themes--mechanobiology, ambulatory mechanics, biomechanical interventions and mechanical risk factors. Novel developments in mechanobiology included the identification of cell signaling pathways that mediated cellular responses to loading of articular cartilage. Studies in ambulatory mechanics included an increased focus on instrumented knee implants and progress in computational models, both emphasizing the importance of muscular contributions to load. Several proposed biomechanical interventions (e.g., shoe insoles and knee braces) produced variable changes in external knee joint moments during walking, while meta-analysis of randomized clinical trials did not support the use of lateral wedge insoles for decreasing pain. Results from high quality randomized trials suggested diet with or without exercise decreased indicators of knee joint load during walking, whereas similar effects from exercise alone were not detected with the measures used. Data from longitudinal cohorts suggested mechanical alignment was a risk factor for incidence and progression of OA, with the mechanism involving damage to the meniscus. In combination, the basic and clinical studies highlight the importance of considering multiple contributors to joint loading that can evoke both protective and damaging responses. Although challenges clearly exist, future studies should strive to integrate basic and clinical research methods to gain a greater understanding of the interactions among mechanical factors in OA and to develop improved preventive and therapeutic strategies., (Copyright © 2014 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Purpose: This narrative review describes experiences at the Fowler Kennedy Sport Medicine Clinic (FKSMC) with high tibial osteotomy (HTO) for patients with varus gonarthrosis, with particular focus on research published from the unit that has guided practice., Methods: The goals of surgery are to improve alignment of the weight bearing axis of the lower limb to lessen the load on the medial tibiofemoral compartment and thereby decrease these important risk factors for disease progression. The overall aims are to improve knee function and delay or even prevent the eventual need for arthroplasty. To achieve these aims, a medial opening wedge osteotomy is utilised, deliberately avoiding an over correction of the lower limb, but tailoring the angle of correction to an individual patient's characteristics. With such an approach, patients with a broad range of characteristics (including age, BMI and lateral compartment involvement) can benefit from the procedure. In addition, the HTO can be used with concomitant procedures to address specific presentations, such as large deformities and instability., Results: The results suggest that correction to a slight valgus alignment produces approximately 50% reduction in medial compartment loads during gait with large, clinically important improvements in patient-reported outcomes at 2-years postoperatively. In patients with substantial bilateral varus deformity, unilateral surgery can lead to increased dynamic knee joint loads on the nonoperative limb after surgery. This means that such patients require the close monitoring of both limbs and consideration of a staged, bilateral procedure if necessary. In patients requiring bilateral surgery, similar results after bilateral HTO to those after unilateral surgery have been reported. For patients requiring large corrections, the need for a concomitant tibial tubercle osteotomy to reduce the potential for iatrogenic patella infera is considered. Finally, HTO procedures can also be used in patients with instability, either to alter both sagittal and coronal alignment to correct instability in complex ligament deficiencies or to undertake simultaneous HTO and ACL reconstruction., Conclusions: HTO is being used both alone and in conjunction with concomitant procedures with good clinical results. While continued investigation into patient selection and outcomes are required, current research indicates that HTO offers at least a partial solution for the patient with varus gonarthrosis to prolong the life of their native knee joint., Level of Evidence: V.

Objectives: (1) Test the hypothesis that walking poles decrease the external knee adduction moment during gait in patients with varus gonarthrosis, and (2) explore potential mechanisms., Design: Thirty-four patients with medial compartment knee osteoarthritis (OA) and varus alignment underwent three dimensional (3D) gait analysis with and without using walking poles. Conditions were randomized and walking speed was maintained ±5% of the self-selected speed of the initial condition. The pole held in the hand of the unaffected side was instrumented with a compression load cell., Results: Student's t tests for paired samples indicated small but statistically significant increases (P < 0.001) in knee adduction moment (calculated from inverse dynamics) for its first peak, second peak and angular impulse when using the poles; mean increases (95% confidence interval - CI) were 0.17%BW*Ht (0.08, 0.27), 0.17%BW*Ht (0.04, 0.30) and 0.15%BW*Ht*s (0.09, 0.22), respectively. There was a decrease (P = 0.015) in vertical ground reaction force (-0.02 BW (-0.04, -0.01)), yet increase (P < 0.001) in its frontal plane lever arm about the knee (0.30 cm (0.15, 0.44)), at the time of the first peak knee adduction moment. Pole force in the vertical direction was inversely related (r = -0.34, P = 0.05) to the increase in first peak adduction moment., Conclusion: Although results are variable among patients, and may be related to individual technique, these overall findings suggest that walking poles do not decrease knee adduction moments, and therefore likely do not decrease medial compartment loads, in patients with varus gonarthrosis. Decreases in knee joint loading should not be used as rationale for walking pole use in these patients., (Copyright © 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Objective: To examine the interaction and relative contributions of frontal plane alignment and body mass on dynamic knee joint loading in patients with knee osteoarthritis (OA)., Methods: We completed three-dimensional gait analyses and hip-to-ankle standing anteroposterior radiographs on 487 patients with knee OA referred to a tertiary care center specializing in orthopaedics., Results: Using sequential (hierarchical) linear regression, the interaction term (mechanical axis anglexmass) contributed significantly (P<0.001) to a model (total adjusted R(2)=0.70) predicting the external knee adduction moment, that included mechanical axis angle (R(2)=0.37) and mass (R(2)=0.06) while controlling for age, sex, height, Kellgren and Lawrence grade, pain score during walking, gait speed, toe out angle and trunk lean (R(2)=0.25). When the sample was split into tertiles for mass, mechanical axis angle accounted for 32-54% of explained variance in knee adduction moment. In the tertile with greatest mass, results suggest a 3.2 N m increase in knee load for every 1 degrees increase in varus alignment. When split into tertiles for mechanical axis angle, mass accounted for 6-10% of explained variance in the knee adduction moment. In the tertile with the most varus alignment, results suggest a 0.4 N m increase in knee load for every 1 kg increase in mass., Conclusion: Our findings describe the interaction between alignment and body mass on dynamic knee joint loading, with the association between alignment and load highest in patients with the highest mass. Our findings also emphasize the role of malalignment on knee load at all levels of mass, and have implications for better understanding risk factors and intervention strategies for knee OA., (Copyright 2010 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Objective: To test the hypothesis that selected gait kinematics, particularly lateral trunk lean, observed in patients with medial compartment knee osteoarthritis explain variation in dynamic knee joint load., Method: In this cross-sectional observational study, 120 patients with radiographically confirmed varus gonarthrosis underwent three-dimensional gait analysis at their typical walking speed. We used sequential (hierarchical) linear regression to examine the amount of variance in dynamic knee joint load (external knee adduction moment) explained by static lower limb alignment (mechanical axis angle) and gait kinematics determined a priori based on their proposed effect on knee load (walking speed, toe-out angle, and lateral trunk lean angle)., Results: Approximately 50% of the variation in the first peak external knee adduction moment was explained by mechanical axis angle (25%), Western Ontario and McMaster Universities Osteoarthritis Index pain score (1%), gait speed (1%), toe-out angle (12%), and lateral trunk lean angle (13%). There was no confounding or interaction with Kellgren and Lawrence grade of severity., Conclusions: Gait kinematics, particularly lateral trunk lean, explain substantial variation in dynamic knee joint load in patients with medial compartment knee osteoarthritis. While largely ignored in previous gait studies, the effect of lateral trunk lean should be considered in future research evaluating risk factors and interventions for progression of knee osteoarthritis.

Objective: To investigate neuromuscular and anatomic factors involved in varus gonarthrosis by identifying measures associated with degenerative changes., Design: Descriptive study. Individual measures that explained substantial portions of the variability in ratings of knee joint-degenerative changes in patients with knee medial compartment osteoarthritis., Setting: Outpatient orthopedic clinic and biomechanics and muscular assessment laboratory., Patients: Volunteer sample of 20 subjects (age range, 59 +/- 9 yr) with no history of neurologic disease., Intervention: Not applicable., Main Outcome Measures: We assessed degenerative changes, varus alignment, standing balance, and knee proprioception. Weight-bearing radiographs were used to assess the extent of degenerative changes and the degree of varus alignment. Single-limb standing balance control was assessed through tests performed on a force platform. Knee proprioception was assessed with an isokinetic dynamometer, using a joint angle replication test., Results: Forward-stepwise multiple linear regression indicated that the extent of degenerative changes could be best predicted from a linear combination of the independent variables, varus alignment, and standing balance (R =.80, F(2,17) = 14.81, p =.0002). Sixty-four percent of the variability in ratings of degenerative changes was explained by alignment and standing balance measures (37% by varus alignment, 27% by standing balance). Alignment and balance measures were poorly correlated (r =.12, p =.63), further suggesting that they provided different information about gonarthrosis., Conclusions: Although varus alignment is widely accepted as a clinically important factor in gonarthrosis, and is the focus of many treatment efforts, our results suggest that objective measures of standing balance are also important. As a result, the potential impact of rehabilitation to improve the control of standing balance should be further evaluated in this patient population.

Objective: To evaluate the effects of a functional knee brace specifically designed for patients with varus gonarthrosis on measures of proprioception and postural control., Subjects: Fourteen men and six women (aged 59+/-9 yr) with measurable varus alignment and osteoarthritis of the knee medial compartment., Methods: Proprioception was assessed in the sitting position using an isokinetic dynamometer and was quantified as the ability to replicate target knee-joint angles. Postural control was assessed with a force platform using tests of single-limb standing balance performed, while the patient was standing on a stable surface and standing on foam, and was quantified as the total length of the path of the centre of pressure. All tests were performed with and without the patient's own custom-fit valgus brace., Results: Proprioception was significantly improved following application of the brace [mean difference=0.7 degrees, 95% confidence interval (CI)=0.2 to 1.1 degrees ). Postural control was not significantly affected by the use of the brace during the stable surface test (mean difference=2.6 cm, 95% CI=-4.3 to 9.5 cm) or the foam surface test (mean difference=0.9 cm, 95% CI=-7.5 to 9.4 cm)., Conclusion: Although enhanced proprioception may be partially responsible for reported improvements with the use of a brace, the present findings call into question the functional importance of the small changes observed.