Objective: To test the hypothesis that a greater peak internal hip abduction moment is associated with a reduced likelihood of ipsilateral medial tibiofemoral osteoarthritis (OA) progression.Methods: Fifty‐seven persons with knee OA (by definite osteophyte presence and symptoms) were evaluated. Baseline assessments included kinematic and kinetic gait parameters, obtained with an optoelectronic camera system and force platform, with inverse dynamics used to calculate 3‐dimensional moments at the joints; pain, using a separate visual analog scale for each knee; and alignment, using full‐limb radiographs. Radiographs of the knee in a semiflexed position, with fluoroscopic confirmation of tibial rim alignment, were obtained at baseline and 18 months later. Disease progression was defined as worsening of the grade of medial joint space narrowing. Logistic regression obtained with generalized estimating equations was used to estimate odds ratios (ORs) for progression per unit of hip abduction moment, after excluding knees with the worst joint space grade at baseline (which could not progress).Results: The 57 participants (63% women) with mild to moderate OA had a mean age of 67 years and a mean body mass index of 29. A greater internal hip abduction moment during gait was associated with a reduced likelihood of medial tibiofemoral OA progression, with OR/unit hip abduction moment of 0.52 and a 95% confidence interval (95% CI) of 0.32–0.85. This protective effect persisted after adjustment for age, sex, walking speed, knee pain severity, physical activity, varus malalignment severity, hip OA presence, and hip OA symptom presence, with an adjusted OR of 0.43 a 95% CI of 0.22–0.81.Conclusion: A greater hip abduction moment during gait at baseline protected against ipsilateral medial OA progression from baseline to 18 months. The likelihood of medial tibiofemoral OA progression was reduced 50% per 1 unit of hip abduction moment.

Objective: To determine whether the presence of varus thrust at baseline increases the risk of progression of medial tibiofemoral osteoarthritis (OA), whether knees with thrust have a greater adduction moment, whether thrust has any additional impact on top of static varus, and whether thrust is associated with poor physical function outcome.Methods: Two hundred thirty‐seven patients with knee OA (definite osteophytes and symptoms) underwent baseline gait observation to assess varus thrust and full‐limb radiography to assess alignment. Sixty‐four of these 237 patients also underwent quantitative gait analysis to determine the maximum knee adduction moment. Two hundred thirty patients (97%) returned for followup at 18 months. At baseline and 18 months, the 230 participants had semiflexed, fluoroscopically confirmed knee radiographs (with progression defined as worsening of medial joint space grade); self‐reported and performance‐based measures of function were also assessed. Logistic regression with generalized estimating equations was used to estimate odds ratios (ORs) for medial OA progression, after excluding knees that were not at risk for progression.Results: Varus thrust was present in 67 of 401 knees. Thrust increased 4‐fold (age‐, sex‐, body mass index–, and pain‐adjusted OR 3.96, 95% confidence interval [95% CI] 2.11–7.43) the odds of medial progression, with some reduction after further adjustment for varus alignment severity. In varus‐aligned knees, thrust increased the odds of OA progression 3‐fold (adjusted OR 3.17, 95% CI 1.60–6.31). In the gait substudy, the adduction moment was greater in knees with a thrust compared with knees without a thrust. Having a thrust in both knees versus neither knee was associated with a 2‐fold increase in the OR for poor physical function outcome (P not significant).Conclusion: Varus thrust is a potent risk factor, identifiable by simple gait observation, for disease progression in the medial compartment, the most common site of OA involvement at the knee. Varus thrust may also predict poor physical function outcome. Varus thrust increased the odds of progression among varus‐aligned knees considered separately, suggesting that knees with a thrust are a subset of varus‐aligned knees at particularly high risk for progression of OA.

Background: A greater knee adduction moment increases risk of medial tibiofemoral osteoarthritis (OA) progression. Greater toe-out during gait shifts the ground reaction force vector closer to the centre of the knee, reducing the adduction moment. The present study was designed to test whether greater toe-out is associated with lower likelihood of medial OA progression. Methods: Baseline assessments included: kinematic/kinetic gait parameters using an optoelectronic camera system, force platform and inverse dynamics to calculate three-dimensional external knee moments; toe-out angle (formed by the line connecting heel strike and toe-off plantar surface centres of pressure and the forward progression line; knee pain; and full-limb alignment. Knee x-rays (semi-flexed) were obtained at baseline and at 18 months, with progression noted as medial joint space grade worsening. With logistic regression, odds ratios (ORs) for progression/5° toe-out were estimated. Results: In the 56 subjects (59% women, mean age 66.6 years, body mass index (BMI) 29), baseline toe-out angle was less in knees with than without progression (difference –4.4, 95% CI –8.5 to –0.3). Greater toe-out was associated with reduced likelihood of progression (OR 0.60, 95% CI 0.37 to 0.98). Adjusting for age, gender, BMI, pain severity and disease severity, the OR was 0.62, 95% CI 0.36 to 1.06. Adjusting for adduction moment (second peak), the OR was 0.72, 95% CI 0.40 to 1.28. Conclusions: Osteoarthritic knees that progressed had less toeing-out than knees without progression. Greater toe-out was associated with a lower likelihood of progression. Adjustment for covariates did not alter the OR, although the 95% CI included 1. Further adjustment for adduction moment did alter the OR, consistent with the possibility that a mechanism of the effect may be via lowering of the adduction moment.

Objective: Varus thrust observed during gait has been shown to be associated with a 4‐fold increase in the risk of medial knee osteoarthritis (OA) progression. Valgus thrust is believed to be less common than varus thrust; the prevalence of each is uncertain. Racial differences in risk factors may help explain variations in the natural history of knee OA. We undertook this study to determine the frequency of varus and valgus thrust in African Americans and Caucasians and to identify factors associated with thrust presence.Methods: The Osteoarthritis Initiative cohort includes men and women who have knee OA or are at increased risk of developing it. Trained examiners assessed thrust presence by gait observation. Logistic regression with generalized estimating equations was used to identify factors associated with thrust presence, and odds ratios (ORs) with 95% confidence intervals (95% CIs) were calculated.Results: Compared with Caucasians, African Americans had lower odds of varus thrust, controlling for age, sex, body mass index (BMI), injury, surgery, disease severity, strength, pain, and alignment in persons without knee OA (adjusted OR 0.50 [95% CI 0.36, 0.72]) and in those with knee OA (adjusted OR 0.46 [95% CI 0.34, 0.61]). Also independently associated with varus thrust were age, sex, BMI, disease severity, strength, and alignment. The odds of valgus thrust were greater for African Americans than for Caucasians in persons without knee OA (adjusted OR 1.69 [95% CI 1.02, 2.80]) and in those with knee OA (adjusted OR 1.98 [95% CI 1.35, 2.91]). Also independently associated with valgus thrust were disease severity and malalignment.Conclusion: Compared with Caucasians, African Americans had lower odds of varus thrust and greater odds of valgus thrust. These findings may help explain the difference between these groups in the pattern of OA involvement at the knee.