Summary. This study shows a significant reduction in knee adduction moment in patients with medial compartment osteoarthritis, in both the symptomatic and asymptomatic knees. Long-term follow-up studies are required to confirm the effect of treating the asymptomatic side on disease progression. Background. The knee is the commonest joint to be affected by osteoarthritis, with the medial compartment commonly affected. Knee osteoarthritis is commonly bilateral, yet symptoms may initially present unilaterally. Higher knee adduction moment has been associated with the development and progression of medial compartment knee osteoarthritis. The aim of this study was to assess the effect of lateral wedge insoles on the asymptomatic knee of patients with unilateral symptoms of medial compartment knee osteoarthritis. Methods. Twenty patients were assessed using a 3D optoelectronic tracking system, with 16 infrared camera, passive markers and four force platforms. Three different insoles were tested; a standard control shoe, the Boston lateral wedge insole (inclined at 5° throughout the full length of the insole) and the Salford insole (inclined at 5° throughout the full length of the insole, with medial arch support). A minimum of 5 trials per each insole were used. Kinetic and kinematic data were collected and processed using Qualysis Track Manager ® and Visual 3D™. Results. There was a significant reduction in knee adduction moment for both the Salford and Boston insoles as compared to the control shoe. This was 9.5–14.2% for the asymptomatic side, and 5.8–10.7% for the symptomatic side for the Salford and Boston insoles respectively. Although the reduction was larger on the asymptomatic side, this was not statistically significant. Patients reported significant reduction in pain with both Salford and Boston insoles as compared to the control shoe, and found the Salford insole to be the most comfortable. Stride length and walking speed was significantly higher with the Salford insole. Conclusions. This study confirms the effect of lateral wedge insoles on reducing knee adduction moment in patients with medial compartment osteoarthritis, in both the symptomatic and asymptomatic knees. Long-term follow-up studies are required to confirm the effect of treating the asymptomatic side on disease progression

Constitutional knee varus increases the risk of medial OA disease due to increase in the knee adduction moment and shifting of the mechanical axis medially. Hueter-Volkmann’s law states that the amount of load experienced by the growth plate during development influences the bone morphology. For this reason, heightened sports activity during growth is associated with constitutional varus due to added knee adduction moment. In early OA, X-rays often show a flattened medial femoral condyle extension facet (EF). However, it is unknown whether this is a result of osteoarthritic wear, creep deformation over decades of use, or an outcome of Hueter-Volkmann’s law during development. A larger and flattened medial EF can bear more weight, due to increased load distribution. However, a flattened EF may also extrude the meniscus, leading meniscus degeneration and joint failure. Therefore, this study aimed to investigate whether varus knees have flattened medial EFs of both femur and tibia in a cohort of patients with no signs yet of bony attrition. Segmentation and morphology analysis was conducted using Materialise software (version 8.0, Materialise Inc., Belgium). This study excluded knees with bony attrition of the EFs based on Ahlbäck criteria, intraoperative findings, and operation notes history. Standard reference frames were used for both the femur and tibia to ensure reliable and repeatable measurements. The hip-knee-angle (HKA) angle defined varus or valgus knee alignment. Femur: The femoral EFs and flexion facets (FFs) had best-fit spheres fitted with 6 repetitions. Tibia: The slopes of the antero-medial medial tibial plateau were approximated using lines. Results 72 knees met the inclusion and exclusion criteria. The average age was 59 ± 11 years. The youngest was 31 and the oldest 84 years. Thirty-three were male and 39 were female. There was good intra- and inter-observer reliability for EF sphere fitting. Femur: The results demonstrated that the medial femoral condyle EF is flattened in knees with constitutional varus, as measured by the Sphere Ratios between the medial and lateral EF (varus versus straight: p = 0.006), and in the scaled values for the medial EF sphere radius (varus versus straight: p = 0.005). There was a statistically significant, moderate and positive correlation between the medial femoral EF radius, and the medial femoral EF-FF AP offset. Tibia: There was a statistically significant difference between the steepness of the slopes of the medial tibial plateau EF in varus and valgus knees, suggesting varus knees have a less concave (flatter) medial EF. Conclusions In comparison to straight knees, varus knees have flattened medial EFs in both femur and tibia. As this was the case in knees with no evidence of bony attrition, this could mean flattened medial EFs may be a result of medial physis inhibition during development, due to Hueter-Volkmann’s law. Flattened medial EFs may increase load distribution in the medial compartment, but could also be a potential aetiology in primary knee OA due to over extrusion of the medial meniscus and edge loading

Abstract. OBJECTIVES. Valgus high tibial osteotomy (HTO) represents an effective treatment for patients with medial compartment osteoarthritis (OA) in a varus knee. However, the mechanisms which cause this clinical improvement are unclear. Previous studies suggest a wider stance gait can reduce medial compartment loading via reduction in the external knee adduction moment (KAM); a measure implicated in progression of medial compartment OA. This study aimed to measure whether valgus HTO is associated with a postoperative increase in static stance width. METHODS. 32 patients, recruited in the Biomechanics and Bioengineering Centre Versus Arthritis HTO study, underwent valgus (medial opening wedge) HTO. Weightbearing pre- and post- operative radiographs were taken showing both lower limbs. The horizontal distance, measured from a fixed point on the right talus to the corresponding point on the left, was divided by the talus width to give a standardised “stance width” for each radiograph. The difference between pre- and post- operative stance width was compared for each patient using a paired sample t-test. RESULTS. Preoperatively, mean stance was 4.00 talar-widths but postoperatively this increased to 5.41. This mean increase of 1.42 talar-widths was statistically significant (p=0.001) and represents a mean proportional increase in stance width of 35.5% following HTO. Of the 32 patients, 23 showed increased stance width and 9 decreased (range −4.64 to 6.00 talar-widths). CONCLUSIONS. These findings indicate an association of frontal plane surgical realignment at the proximal tibia via a medial opening wedge HTO with an increased stance width on postoperative radiographs. Considering both wider stance gait and HTO have been shown to affect the progression of medial compartment OA, these results may explain one mechanism contributing to the efficacy of HTO surgery. However, the range of changes in stance width suggests significant variability in how patients adapt at a whole-limb and whole-body level following HTO. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Abstract. Objective. Explore whether high tibial osteotomy (HTO) changes knee contact forces and to explore the relationship between the external knee adduction moment (EKAM) pre and 12 months post HTO. Methods. Three-dimensional gait analysis was performed on 17 patients pre and 12-months post HTO using a modified Cleveland marker-set. Tibiofemoral contact forces were calculated in SIMM. The scaled musculoskeletal model integrated an extended knee model allowing for 6 degrees of freedom in the tibiofemoral and patellofemoral joint. Joint angles were calculated using inverse kinematics then muscle and contact forces and secondary knee kinematics were estimated using the COMAC algorithm. Paired samples t-test were performed using SPSS version 25 (SPSS Inc., USA). Testing for normality was undertaken with Shapiro-Wilk. Pearson correlations established the relationships between EKAM1 to medial KCF1, and EKAM2 to medial KCF2, pre and post HTO. Results. Total knee contact force peak 1 significantly reduced from 2.6 x body weight pre-HTO to 2.3 x body weight 12-months post-HTO. Medial contact force peak 1 significantly reduced from 1.7 x body weight pre-HTO to 1.5 x body weight 12-months post-HTO. Second peak lateral knee contact force significantly increased from 0.9 body weight pre-HTO to 1.1 x body weight 12-months post-HTO. Furthermore, this study found very strong correlations between EKAM1 and medial KCF1 pre-HTO (r=0.85) as well as post-HTO (r=0.91). There was a significantly moderate relationship between EKAM2 and medial KCF2 pre-HTO (r=0.625). Conclusion. HTO significantly reduced overall and medial KCF during the first half of stance whilst increasing second half of stance peak lateral knee contact force. This study demonstrated a strong relationship between EKAM peaks and respective medial KCF peaks, supporting the usefulness of EKAM as a surrogate measure of medial compartment tibiofemoral contact forces. This demonstrates HTO successfully offloads the tibiofemoral joint overall, as well as offloading the medial compartment

Osteoarthritis is one of the major causes of immobility. Most commonly, osteoarthritis manifests at the knee joint. Prevalence of knee osteoarthritis (KNOA) increases with age. Another important risk factor for KNOA is obesity. Research has shown that obese subjects have almost four times the risk of developing KNOA, which may be explained by both an increased knee loading. In medial compartment KNOA, the knee adduction moment (KAM) during gait is considered a marker for disease severity. KAM is dependent of the magnitude of the ground reaction force and its moment arm relative to the knee joint centre. In addition, obesity has been reported to augment KAM during gait. However, after removal of the direct contributions of body weight, KAM parameters may be different due to obesity-related gait adaptations to limit knee loading. While KAM has been thoroughly investigated during gait, little is known about KAM during stair negotiation, during which knee loads are higher compared to gait. The aim of the current study is therefore to compare normalized KAM during the stance phase of stair negotiation between lean KNOA patients, obese KNOA patients, and healthy controls. This case control study included 20 lean controls, 14 lean KNOA patients, and 16 obese KNOA patients. All subjects ascended and descended a two-step staircase at a self-selected, comfortable speed. Radiographic imaging and MRI were used to evaluate knee cartilage and KNOA status. Motion analysis was performed with a three-dimensional motion capture system. Kinetic data were obtained by one force platform. The parameters of study included: stance phase duration, toe-out angle, KAM peaks and KAM impulse. During stair ascent obese KNOA patients showed a longer stance phase than healthy controls (P 0.050). Despite high between-subject variability, KAM impulse was found 45% higher in the obese KNOA group during stair descent, when compared to healthy controls (P =0.012). The absence of a significant effect of groups on the normalized KAM during stair negotiation may be explained by a lower ambulatory speed in the obese KNOA group, that effectively lowers GRFz. Decreasing ambulatory speed may be an effective strategy to lower KAM during stair negotiation

Osteoarthritis is a multifactorial disease in which altered mechanical loading is one of the agreed contributing factors. Whereas in the past, altered mechanical loading was merely deferred from static, image-based evaluations of malalignment, the recent use of 3D motion capture allowed dynamic evaluation of joint loading in terms of dynamic alignment (e.g. varus trust) and even joint loading strategy (merely using proxy measures like knee adduction moment.) Combining these measurements with musculoskeletal models, the overall loading distribution in the joint due to muscle action underlying the patient's motion pattern can be quantified. Using this approach, our group showed the potential of this technique to differentiate between control subjects and subjects with early medial knee OA before the presence of radiographic evidence of structural joint degradation. Nevertheless, no changes in loading distribution could be detected in a cohort of subjects suffering of local cartilage defects in an otherwise healthy knee joint, indicating that patients did not present active unloading strategies despite the presence of clinical symptoms. Furthermore, subject-specific strategies aiming contributing to modified loading of the hip joint have been evaluated

Knee osteoarthritis (OA) is a serious health concern, requiring novel therapeutic options. Walking mechanics has long been identified as an important factor in the OA process. Specially, a larger peak knee adduction moment during the first half of stance (KAM) has been associated with the progression of medial knee OA. Consequently, various gait interventions have been designed to reduce the KAM, including walking with a decreased foot progression angle (FPA). Other gait variables have recently been associated with medial knee OA progression, particularly a larger peak knee flexion moment during stance (KFM) and a larger knee flexion angle at heel-strike (KFA). Currently, there is a paucity of data regarding the effect of reducing the FPA on the KFM and KFA. This study aimed to test for correlations between the FPA and the KAM, KFM and KFA. It was hypothesized that reducing the FPA is beneficial with respect to these three OA-related gait variables. Seven healthy subjects participated in this study after providing informed consent (4 male; 24 ± 5 years old; 21.9 ± 1.5 kg/m^2). Their walking mechanics was determined using a validated procedure based on a camera-based system (Vicon) and floor-mounted forceplates (Kistler). Participants were first asked to walk without instructions and these initial trials were used to determine their normal footstep characteristics. Then, footsteps with the same characteristics as during the normal trials, except for the FPA, were displayed on the floor and participants were requested to walk following these footsteps. Nine trials with visual instructions were collected for each participant, corresponding to FPA modifications in the range ± 20° compared to the normal FPA, with 5° increment. For each participant, the associations between FPA and knee biomechanics (KAM, KFM and KFA) were assessed using Pearson correlations based on the data from the 9 trials with FPA variations. Significant level was set a priori to 5%. Significant correlations were noted between FPA and KAM for 5 out of the 7 participants, with R comprised between 0.75 and 0.96. Four participants also reported significant correlations between FPA and KFA (−0.88<R<−0.69). Significant correlations between FPA and KFM were observed in 2 participants, with inconsistent R (−0.68 and 0.78). There was no significant correlation between FPA and walking speed for none of the participants. While the results confirmed that decreasing the FPA (toeing in) is often associated with a KAM reduction, they also showed relationships between decreased FPA and increased KFA. Therefore, this study suggests that reducing the FPA should be done in consideration of the possible negative changes in KFA. Similarly, although only one participant increased the KFM when decreasing the FPA, it seems important monitoring the effects FPA modifications could have on the KFM. The large variations observed among participants further suggest individualized gait modifications. This study should be extended to medial knee OA patients and longitudinal research is necessary to better understand the effects of decreasing the FPA

Summary. The quantification of T1Rho relaxation times is not related with internal loading. Improvements in modeling and imaging techniques might lead to better understanding of the pathomechanics of the knee. Introduction. The onset and progression of knee osteoarthritis has been associated with an increased external knee adduction moment (EKAM). However, this external measure has no direct relationship with internal loading of the knee. For a better understanding of the pathomechanics of the knee musculoskeletal models could be used to relate external and internal knee loading. Consequently, high internal loading might cause cartilage degeneration in patients with OA. T1RhoMRI can detect changes in proteoglycan content and is therefore a non-invasive measure of cartilage degeneration in knee OA. The purpose of this study was to relate internal loading of the knee simulated by musculoskeletal models with cartilage health using T1rhoMRI. Patients & Methods. Preliminary results showed data of seven women (50–65yrs), four healthy and three OA. Subjects underwent 3D gait analysis (VICON Nexus) at comfortable walking speed, EKAM was calculated. Simulations of multi-body musculoskeletal models were driven based on the motion capture data, in order to calculate internal medial-lateral knee forces (MLforce). Besides a T1RhoMRI scan of the knee (Phillips 3T) provided cartilage health of the midsection of the medial condyle according to Pedersen et al, 2011 [4]. Differences between healthy and OA were tested with a one sided T-test, correlations between EKAM and MLforce were calculated. Results. Anthropometrics and walking speed showed no significantly different between OA patients and healthy controls. OA patients had significant larger EKAM and MLforce (p<0.05). T1Rho values were not significantly different between the groups. EKAM was positively correlated with MLforce (R. 2. =0.91, p<0.05) in healthy subjects, no association was found in knee OA patients (R. 2. < 0.01). Discussion / Conclusion. The current study demonstrates that external loading of the knee does not predict internal loading in knee OA patients. We did not find a significant effect of knee OA on cartilage quality assessed by T1Rho MRI. However a non-significant increase was visible at the posterior region of the femoral condyle in OA patients. This elevated T1Rho relaxation is in line with expectations and could be related to an increased cartilage degeneration

BACKGROUND. High tibial Osteotomy (HTO) realigns the forces in the knee to slow the progression of osteoarthritis. This study relates the changes in knee joint biomechanics during level gait to glutamate signalling in the subchondral bone of patients pre and post HTO. Glutamate transmits mechanical signals in bone and activates glutamate receptors to influence inflammation, degeneration and nociception in arthritic joints. Thus glutamate signalling is a mechanism whereby mechanical load can directly modulate joint pathology and pain. METHODS. 3D motion analysis was used to assess level gait prior to HTO (n=5) and postoperatively (n=2). A biomechanical model of each subject was created in Visual3D (C-motion. Inc) and used for biomechanical analysis. Gene expression was analysed by RT-PCR from bone cores from anterior and posterior drill holes, subdivided according to medial or lateral proximal tibia from HTO patients (n=5). RESULTS. Knee adduction moment is a clinical marker of medial compartment loading. Pre-operatively the mean peak adduction moment was 3.8 ± 1.8 % body weight times height (BW.h). One subject maintained a consistent peak adduction moment pre (1.8 %BW.h) and post-operatively (1.9 %BW.h) with a reduction in the second moment peak. Another subjects peak adduction moment was significantly reduced from 6.7 %BW.h pre-operatively to 1.4 %BW.h postoperatively. GAPDH, osteocalcin, EAAT-1, EAAT1ex9skip, NR2A, KA1, OPG and RANKL mRNA expression was detected in HTO bone cores. In one patient, where HTO reduced medial compartment loading, differential expression of EAAT1ex9skip and KA1 was observed in pre and post HTO bone cores. CONCLUSION. Changes in knee adduction moments following HTO have been identified indicating altered medial compartmental loading. This is being investigated further in larger cohorts in a 5 year study. We have demonstrated that glutamate transporters and receptors are expressed in human subchondral bone and that glutamate transporter mRNA expression may vary after HTO surgery. In arthritis, glutamate concentrations in the synovial fluid are increased, activating receptors in joint tissues and nerves to influence pathology and nociception. Thus glutamatergic signals represent a direct mechanism linking mechanical loading through the joint to pathology and pain in human arthritis

Summary Statement. This study provides preliminary evidence that people with knee osteoarthritis have greater asymmetry in joint loading than healthy controls. Altered loading of the contralateral limb may signify increased risk of injury to other lower limb joints in knee osteoarthritis. Introduction. Compensatory overloading of other lower limb joints is a potential reason for the non-random evolution of osteoarthritis (OA). In individuals with knee OA altered joint loading exists of the contralateral cognate joints. However, previous studies have neglected the temporal features of asymmetry in joint loading. The study aimed to identify the amount and temporal features of asymmetry in lower limb joint loading in advanced knee OA. Patients and Methods. Participants (n=15) were awaiting primary unilateral total knee replacement for OA (age 67.0 SD 8.9 years, height 1.66 SD 0.13 m, mass 84.2 SD 15.8 kg, BMI 30.7 SD 6.2 kg/m. 2. , median KL grade 4). Data were compared to asymptomatic age and sex matched controls. Kinematic and kinetic data during walking was acquired with 12 cameras (VICON MX-F20) and two Kistler force platforms at 100 Hz and 400 Hz respectively. Data were analysed in Visual3D (C-Motion Inc., USA). Asymmetry was computed in MatLab using a recently published symmetry index (SI) and symmetry function (SF). Variables (computed using inverse dynamics) were the peak external moments (%BW∗Height) of the hip, knee and ankle. Differences between means of the SI variables in the OA and control groups were compared using Student's t-tests. Discrete variables were also compared between limbs (paired t-test) or between the affected limb and matched control limb. Effect sizes (Cohen's d) for the differences were also computed. Results. A significant between group difference (OA and control) for SI was observed for the transverse plane ankle joint moment (16.1 SD 8.0 vs. 10.4 SD 4.8 d = 0.8 p = 0.049). A large effect size for the sagittal plane knee joint moment (22.9 SD 12.1 vs. 12.7 SD 5.1 d = 1.1 p = 0.178) and a medium effect size for the transverse plane hip joint moment (26.4 SD 15.9 vs. 16.6 SD 9.0 d = 0.7 p = 0.098) were observed. The unaffected limb (OA group) had higher peak hip flexion (5.76 SD 1.49 vs.5.32 SD 1.51 p = 0.041) and internal rotation moments (−0.67 SD 0.34 vs. −0.41 SD 0.18 d = 0.004) and a lower ankle inversion moment (0.16 SD 0.14 vs. 0.34 SD 0.24 d = 0.9 p = 0.030) compared to the affected limb. Only the difference in the first peak knee adduction moment for the affected and matched control limb was statistically significant (−2.65 SD 1.38 vs. −2.16 SD 1.16 d = 0.7 p = 0.031). Discussion and Conclusion. This study provides preliminary evidence of more asymmetry in joint moments of the lower limb in people with knee OA compared to controls. Further investigation with a larger sample is required to verify these findings. Altered loading of the contralateral cognate joints may signify increased risk of injury at the hip and ankle and highlights the need for monitoring of other lower limb joints in knee OA