Functional Recovery After Total Knee Arthroplasty

Osteoarthritis (OA) of the knee is one of the most prevalent age-related musculoskeletal conditions, resulting in significant impairment in patients' abilities to perform activities and adversely impacting their quality of life. The level of impairment in patients with knee OA can be measured using validated self-report questionnaires, such as the disease-specific Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the generic Medical Outcomes Study Short Form-36 (SF-36). Self-report questionnaires have been recommended by some investigators for their high internal consistency and ease of administration. Another method to evaluate physical function in patients with knee OA is to use performance-based tests. These tests are tools that assess patients' ability to execute a task in a standardized environment, and include the 2-minute walk test (2MWT) and the timed get-up-and-go test (TUG).

Among all the self-reported questionnaires for knee OA, the WOMAC is one of the most commonly used for baseline assessment and for measurement of treatment outcome, and has been validated for patients undergoing total knee arthroplasty (TKA). Although the WOMAC provides information on how individuals perceive their physical function in their own environment, it does not describe their ability to perform a specific task or action. In addition, some investigators showed that scores from self-report questionnaires before and after arthroplasty can overestimate patients' actual functional capacity. For example, Parent et al demonstrated that total knee arthroplasty patients had a dramatic improvement at 2 months as assessed by the WOMAC function subscale, however there were no significant changes when measured with performance-based tests assessing gait speed and stair ascent duration. Therefore, clinicians should be cautious when interpreting findings from studies that provide only self-report questionnaire scores. Given that self-report questionnaires may over-estimate functional status after joint replacement, some authors advocate performance-based tests as measures of outcome, and recommend their use during the preoperative period as baseline measurements followed by subsequent comparison with postoperative measurements.

The objectives of this study are: 1) to assess the relationship between self-reported questionnaires (WOMAC and SF-36) and performance-based tests (2MWT, TUG) among patients scheduling for TKA; and 2) to identify clinical variables that are associated with pre- and post-operative performance of the 2MWT and TUG. Our hypothesis is that correlations between self-report questionnaires and performance-based tests would be low to moderate, and thus these two types of measurements evaluate distinct domains of functional status in patients undergoing TKA.