Association of Varus Thrust With Pain and Stiffness and Activities of Daily Living in Patients With Medial Knee Osteoarthritis

Background. Increasing evidence highlights potential associations between varus thrust and health domains associated with knee osteoarthritis (OA). Objective. The aim of this study was to investigate the association between varus thrust and 2 subcategories-"pain and stiffness" and "activities of daily living (ADL)"-of the Japanese Knee Osteoarthritis Measure (MOM). Design. This was a cross-sectional study. Methods. In total, 296 outpatients with knee OA visiting orthopedic clinics were enrolled. The inclusion criteria were age >= 50 years, medial knee OA and Kellgren-Lawrence (K/L) grade >= 1 in one or both knees, and the ability to walk independently. Standard posterior-anterior knee radiographs were measured for varus alignment. Participants were video recorded while walking and were evaluated for the presence or absence of yams thrust. Pain and stiffness of the knee joint and ADL were evaluated using the JKOM. Multivariate regressions (outcomes: pain and stiffness and ADL; predictor variable: varus thrust) were performed. Results. Yams thrust was present in 46 (16.2%) of 284 patients. Multivariate regression analyses demonstrated that varus thrust is independently associated with pain and stiffness, adjusted for age, sex, body mass index, K/L grade, and varus alignment (beta=.17, P=.005). However, the association between varus thrust and ADL was not significant (beta=.11, P=.058). Based on sensitivity analyses, including participants of K/L grade 1 had little influence on this analysis. Limitations. Only 16.2% of participants had a varus thrust. Moreover, a cause-effect relationship between varus thrust and pain and stiffness remains unknown due to the cross-sectional design of this study. Conclusions. Yams thrust was associated with pain and stiffness in patients with medial knee OA. However, the association between varus thrust and ADL did not reach significance.