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Background: There is limited understanding of how antagonist muscle coactivation relates to measurement of strength in both individuals with and without knee osteoarthritis (KOA).Objective: This study sought to determine whether hamstring coactivation during a maximal quadriceps activation task attenuates net quadriceps strength.Design: Cross-sectional cohort analysis was conducted using data from the 60-month visit of the Multicenter Osteoarthritis Study (MOST).Setting: Laboratory.Participants: A sample of 2328 community-dwelling MOST participants between the ages of 55 and 84 years, with or at elevated risk for KOA, completed the 60-month MOST follow-up visit. Of these, 1666 met inclusion criteria for the current study.Interventions: Not applicable.Main Outcome Measure(s): Quadriceps strength; percentage of combined hamstring coactivation (HC), medial HC, and lateral HC. Quadriceps and hamstring strength were assessed using an isokinetic dynamometer. Surface electromyography was used to assess muscle activation patterns. General linear models, adjusted for age, BMI, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Kellgren-Lawrence (KL) grade and study site, modeled the relationship between antagonist hamstring coactivation and quadriceps strength.Results: Men had significantly greater quadriceps strength (P < .001), history of knee injury (P < .001) and surgery (P = .002), and greater presence of varus malalignment (P < .001). Women had greater pain (P < .001) and proportion of KL grade ≥2 (P = .017). Gender-specific analyses revealed combined HC (P = .013) and lateral HC inversely associated with quadriceps strength in women (P = .023) but not in men (combined HC P = .320, lateral HC P = .755). A nonlinear association was detected between quadriceps strength and medial HC. Assessment of quartiles of medial HC revealed the third quartile had reduced quadriceps strength when compared to the lowest quartile of coactivation in both men and women.Conclusions: Hamstring coactivation attenuates measured quadriceps strength in women with or at elevated risk for KOA.Level Of Evidence: II. [ABSTRACT FROM AUTHOR]

Limitations of plain radiographs may contribute to poor sensitivity in the detection of knee osteoarthritis and poor correlation with pain and physical function. Three‐dimensional (3D) joint space width (JSW), measured from weight‐bearing computed tomography (CT) images, may yield a more accurate correlation with patients' symptoms. We assessed the cross‐sectional association between 3D JSW and self‐reported pain and physical function. Five hundred twenty eight knees (57% women) were analyzed from Multicenter Osteoarthritis Study participants. An upright weight‐bearing CT scanner was used to acquire bilateral, weight‐bearing, fixed‐flexion images of the knees. A 3D dataset was reconstructed from cone beam projections and JSW was calculated across the joint surface. The percentages of the apposed medial tibiofemoral joint surface with JSW less than 2.0 and 2.5 mm, respectively, were calculated. Pain and physical function were measured using Western Ontario and McMaster Universities Osteoarthritis Index. Participants who reported greater pain severity tended to have a greater joint area with JSW less than 2.0 mm (P =.07 for the highest vs the lowest tertile). Participants who reported greater functional limitations had a greater joint area with JSW less than 2.0 mm (P =.02 for the highest vs the lowest tertile). There appears to be an association between the medial tibiofemoral area with JSW less than 2.0 mm and pain and physical function. [ABSTRACT FROM AUTHOR]

Supplemental digital content is available in the text. Objective: The aim of the study was to determine whether tibiofemoral contact stress predicts risk for worsening knee pain over 84 ms in adults aged 50–79 yrs with or at elevated risk for knee osteoarthritis. Design: Baseline tibiofemoral contact stress was estimated using discrete element analysis. Other baseline measures included weight, height, hip-knee-ankle alignment, Kellgren-Lawrence grade, and Western Ontario and McMaster Universities Osteoarthritis Index pain subscale. Logistic regression models assessed the association between baseline contact stress and 84-mo worsening of Western Ontario and McMaster Universities Osteoarthritis Index pain subscale. Results: Data from the dominant knee (72.6% Kellgren-Lawrence grade 0/1 and 27.4% Kellgren-Lawrence grade ≥ 2) of 208 participants (64.4% female, mean ± SD body mass index = 29.6 ± 5.1 kg/m2) were analyzed. Baseline mean and peak contact stress were 3.3 ± 0.9 and 9.4 ± 4.3 MPa, respectively. Forty-seven knees met the criterion for worsening pain. The highest tertiles in comparison with the lowest tertiles of mean (odds ratio [95% confidence interval] = 2.47 [1.03–5.95], P = 0.04) and peak (2.49 [1.03–5.98], P = 0.04) contact stress were associated with worsening pain at 84 mos, after adjustment for age, sex, race, clinic site, and baseline pain. Post hoc sensitivity analyses including adjustment for body mass index and hip-knee-ankle alignment attenuated the effect. Conclusions: These findings suggest that elevated tibiofemoral contact stress can predict the development of worsening of knee pain. [ABSTRACT FROM AUTHOR]