A COMPARISON OF PHYSICAL ACTIVITY EXPECTATIONS BETWEEN TWO COHORTS WITH KNEE OSTEOARTHRITIS

Background: Fulfillment of patient expectations is an important factor affecting health outcomes. Few studies have examined physical activity (PA) in individuals with knee osteoarthritis (OA) after total knee arthroplasty (TKA).Objectives: The purpose of this cohort study was to compare actual with expected PA between two cohorts with knee OA, one undergoing TKA (TKA Cohort) and one not undergoing TKA (Non-TKA Cohort).Methods: Data on sociodemographic, clinical, health status, and physical activity characteristics were collected at baseline using standardized structured interviews and self-administered questionnaires. Clinical characteristics included body mass index (BMI), comorbidities (Charlson Index), and disease severity (Index of Severity for Knee Disease). The Short-Form Health Survey (SF-36) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were used to determine general and disease-specific health status, respectively. The Historical Leisure and Modifiable Activity Questionnaires were used to assess past-month total PA (leisure and occupational activity combined) at baseline (actual PA and expected PA at 12 months) and 12 months later (actual PA). An Analysis of Covariance (ANCOVA) was performed to control for important variables when examining differences in expectations between the cohorts.Results: There were 29 (34.9%) males and 54 (65.1%) females in the TKA Cohort with a mean age of 66.5±9.7 years. The Non-TKA Cohort contained 20 (24.4%) males and 62 (75.6%) females with a mean age of 68.5±10.4 years. The TKA Cohort was more obese and reported higher levels of pain, stiffness, and functional limitations than the Non-TKA Cohort (p<0.01). At baseline, the Non-TKA Cohort reported more total PA than the TKA Cohort (median 37.4 MET-hours per week versus 23.9, p=0.001). Although the TKA Cohort reported more actual PA than the Non-TKA Cohort at 12 months (p=0.01), there was no difference in physical activity expectations between the cohorts (p=0.07). At 12 months, there was no difference between actual and expected total PA in the TKA Cohort, indicating that the cohort met their physical activity expectations (median 52.4 actual MET-hours per week versus 57.6 expected, p=0.20). The Non-TKA Cohort, however, was less active than expected (median 40.7 actual MET-hours per week versus 45.1 expected, p<0.01). The discrepancy between actual and expected PA was similar in each cohort (p=0.83). An ANCOVA indicated that baseline total PA (regression coefficient [b]=0.81, p<0.001), general health (b=0.4, p=0.048), BMI (b=1.7, p=0.002), use of assistive device when ambulating (yes versus no) (b=12.4, p=0.004), and cohort (TKA versus Non-TKA) (b=-18.5, p<0.001) were significant in explaining the variation in expected total PA at 12 months (R=0.47).Conclusion: The TKA Cohort expected to perform 18.5 more MET-hours of total PA per week 12 months after surgery than those who did not undergo TKA. Activity expectations were greater in those who were more active at baseline, had a higher BMI, were able to ambulate without an assistive device, and reported better general health. The TKA Cohort met their PA expectations, however, an educational intervention may be needed in people with knee OA and no planned surgery to help establish appropriate PA goals.Citation: Ann Rheum Dis, volume 66, supplement II, year 2007, page 279Session: Health service and outcome research