Determinants of 6-Minute Walk Test Performance in Individuals with Knee Osteoarthritis

Objectives Knee osteoarthritis (OA) is a leading cause of physical disability worldwide. Assessing physical function is important to guide treatment. The 6-minute walk test (6MWT), recommended by the Osteoarthritis Research Society International (OARSI) as a performance-based measure of physical function,[1] was originally developed to assess submaximal aerobic fitness in people with cardiovascular and respiratory disease. In knee OA, evidence regarding its association with other measures of OA-related function is inconsistent,[2,3] raising uncertainty about the degree to which 6WMT performance reflects knee OA severity vs other patient-related factors. In individuals with symptomatic knee OA scheduled for primary total knee arthroplasty (TKA), this study assessed the contributions of OA-related and non-OA-related patient factors to 6MWT distance. Methods In this cross-sectional study within the Alberta BEST-Knee cohort, participants with symptomatic knee OA scheduled for primary TKA completed a standardized questionnaire assessing sociodemographic factors (age, sex, level of education), patient-reported knee OA symptoms (WOMAC pain, KOOS-PS), comorbidities (number of symptomatic lower extremity joints, lower back pain, number of non-MSK comorbidities, BMI), and psychosocial factors (PHQ-8 depressive symptoms, arthritis coping). A subset of participants additionally completed the 6MWT prior to surgery. The characteristics of those who completed the 6MWT were compared by tertiles of 6MWT distance. Multivariable linear regression modeling was used to assess the contribution of OA-related and non-OA patient factors to 6MWT distance. Results Among 278 participants (mean age 67 years, 65% female), individuals in the lowest tertile of 6MWT distance were more likely to be older, female, not have post-secondary education, report more comorbidities, have higher BMI, more depressive symptoms, poorer arthritis coping, greater perceived difficulty walking, higher WOMAC pain, worse KOOS-PS, and were more likely to be using a gait aid than those in the middle and uppermost tertiles. In multivariable analysis, lower scores for knee pain and disability, younger age, male sex, lower BMI, fewer non-musculoskeletal comorbidities, post-secondary education, and greater perceived arthritis coping were associated with greater 6MWT distance (Table 1). Low back pain, number of other troublesome joints, or depressive symptoms were not independently associated with 6MWT distance. Table 1. Multivariable Linear Regression Analysis of the Association Between Knee Osteoarthritis Patient Factors and Six-Minute Walk Test Distance Conclusion While 6MWT distance declines with greater knee OA symptom severity, other biomedical and psychosocial factors also significantly influence 6MWT performance. These factors should be considered when using and interpreting the 6MWT in this population. References [1.] Dobson F. Osteoarthritis Cartilage 2013;46:981-9. [2.] Maly MR. J Arthroplasty 2011;26:728-37. [3.] Lee SH. BMC Musculoskelet Disord 2022;23:1040.