VanSwearingen JM, Brach JS, Hicks G; Department of Physical Therapy, University of Pittsburgh, PA. jessievs@pitt.edu.

Documenting clinical status and response to intervention for persons with knee osteoarthritis (OA) at the impairment and disability levels have been limited by the bias of self report measures of pain and disability. PURPOSE: To determine the reliability of performance-based measure of lower extremity function in women with knee OA. SUBJECTS: Thirty five women participating in a study of a disease modifying drug volunteered to participate. Women studied were a mean age of 55.9, SD, 5.4, range, 47.5-65.2 years; all women were overweight (upper tertile of body mass index). METHODS: Performance-based measures of impairment and disability included: muscle activity of the quadriceps and hamstring muscle groups recorded with surface electromyography (sEMG) during performance of the physical function task of chair stand; gait speed recorded electronically at a self-selected and fast pace using the GaitMat II. DATA ANALYSIS: Intraclass correlation coefficients, ICC (2,1) were used to determine test-retest (for trials repeated after removal and replacement of electrodes), and inter rater reliability for the peak sEMG, time-to-peak sEMG and slope of the rise-to-peak recorded during chair stand. Test-retest reliability for gait speed measures was determined using ICC (2,1) for consecutive trials and delayed repeated trials of gait speed. RESULTS: Preliminary results of test-retest reliability for the measure of sEMG of the right quadriceps muscle group during chair stand was peak, ICC=.72, CI,.52,.85; time to peak, ICC=.39, CI,.07,.63; slope of rise, ICC=.49, CI,.20,.71. Inter rater reliability for a subset of the cases (n=11) for sEMG values recorded for the right quadriceps was peak, ICC-,99, CI,.99,.99; time-to-peak, ICC=.91, CI,.72, .98; slope of rise, ICC=.87, CI,.61,.96. Test-retest reliability for consecutive trials of gait speed at usual pace was ICC=.93, CI,.84,.97; fast pace, ICC=.84, CI,.67,.92. For delayed repeated trials of gait, test-retest reliability at usual pace was ICC=.74, CI,.49,.87; at fast pace, ICC=.73, CI,.48,.87. CONCLUSION: Performance-based measures of impairment (muscle activity during chair stand) and disability (gait speed) can be reliably determined and have the potential for use in describing outcome of intervention for women with OA of the knee. FUNDING SOURCE: (The project was partially funded by the CMRF, University of Pittsburgh Medical Center.)

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