Comparing the predictive value of task performance and task-specific sensitivity during physical function testing among people with knee osteoarthritis

STUDY DESIGN: Cross-sectional cohort. BACKGROUND: Knee osteoarthritis (OA) is a leading cause of pain and mobility restriction. Past research has advocated the use of brief, functional tasks to evaluate these restrictions, such as the six-minute-walk test and the timed up-and-go test. Typically, only task performance (ie, walking distance, completion time) is used to inform clinical practice. Recent research, however, suggests that individual variance in how people feel while completing these tasks (ie, task sensitivity) might also have important clinical value. OBJECTIVE: To compare the predictive value of task performance and task-specific sensitivity in determining OA-related physical function (measured by the Western Ontario and McMaster Universities Osteoarthritis Index) and pain-related interference (measured by the Multidimensional Pain Inventory). METHODS: One hundred eight participants with chronic knee OA completed the six-minute-walk test and the timed up-and-go test, and reported levels of discomfort and affective response (mood) associated with each test. RESULTS: In separate regression models, both task performance and task-specific sensitivity predicted OA-related physical function and pain-related interference. A final regression model including all significant predictors showed that task-specific sensitivity (specifically, post sixminute- walk discomfort) emerged as a unique predictor of both outcomes. CONCLUSION: These findings highlight the value of a novel clinical assessment strategy for patients with knee OA. While clinicians commonly focus on how patients perform on standardized functional tasks, these results highlight the value of also considering levels of posask sensitivity. Measures of task-specific sensitivity relate to Maitland s concept of pain irritability, which may be a useful framework for future research on sensitizing factors and pain-related disability.