Longitudinal Relationship Between Tibiofemoral Contact Stress at Baseline and Worsening of Knee Pain Over 84 Months in the Multicenter Osteoarthritis Study.

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/m 2 ) 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.

Effect of a Realigning Brace on Tibiofemoral Contact Stress.

OBJECTIVE: To determine the degree to which focally elevated tibiofemoral joint contact stress is reduced by using a frontal plane realigning brace. METHODS: Fifteen volunteers (9 women) with unicompartmental tibiofemoral osteoarthritis underwent weight-bearing radiographic imaging at 15-20° and 5-10° of knee flexion with and without an UnloaderOne knee brace. Discrete element analysis was used to estimate compartment-specific contact stress distributions. Paired t-tests were used to assess the differences in mean contact stress and contact stress distributions, comparing the braced and unbraced conditions. RESULTS: The mean ± SD age was 56.1 ± 6.4 years and body mass index was 28.4 ± 4.5 kg/m(2). Twelve of 15 participants were fit with braces set to unload the medial compartment. For the 15-20° condition, the mean contact stress in the compartment of interest did not significantly change (0.08 ± 0.35 MPa; P = 0.410). Also at 5-10° flexion, the mean contact stress in the compartment of interest did not significantly change with use of the brace (0.24 ± 0.45 MPa; P = 0.175). CONCLUSION: This is the first study of the effects of a frontal plane realignment brace on in vivo articular contact stress in native human knees. Using the off-the-shelf brace tested, there were no changes in compartmental tibiofemoral contact stress distributions at either 15-20° or 5-10° of knee flexion, revealing no redistribution of contact stress away from the compartment of interest. These findings indicate that the brace that was studied was ineffective for redistributing tibiofemoral contact stress. Further research is necessary to determine whether double-upright or customized frontal plane braces are effective in redistributing compartmental articular contact stress.