We determined whether the sensitivity to change of the Western Ontario McMaster Osteoarthritis Index (WOMAC) physical function (PF) subscale, a condition-specific measure for persons with osteoarthritis of the hip or knee, was superior to a lower extremity region-specific measure, the Lower Extremity Functional Scale (LEFS), in persons with osteoarthritis of the hip or knee undergoing total joint arthroplasty.
The WOMAC and LEFS were administered to 102 patients with osteoarthritis preoperatively, within 16 days of surgery, and >20 days after the first postoperative assessment. These time points enabled the assessment of deterioration and improvement. Two timed performance measures (40 m walk test and the timed-up-and-go test) were also assessed. Change was quantified by the standardized response mean (SRM).
WOMAC PF SRMs were not greater than the LEFS SRMs. Performance measures' times increased significantly over the deterioration interval and decreased over the improvement interval. The WOMAC PF and LEFS demonstrated significant improvement over the second assessment interval; only the LEFS showed significant deterioration over the first assessment interval. WOMAC PF scores seem to be strongly influenced by pain.
The findings do not support the hypothesis that the WOMAC PF subscale is superior to the LEFS in detecting change.