Olson SL, Deshpande AM, Conditt M, Noble PC, Parsley BS; Texas Woman’s University and Baylor College of Medicine, Houston, Texas, USA. solson@twu.edu.

PURPOSE: The purpose of this study was to assess the test-retest reliability and construct validity of 18 physical performance tests previously shown to be difficult for persons with total knee arthroplasty (TKA) as compared to an age-matched group of subjects with no lower extremity problems. SUBJECTS: The 20 subjects, 7 men and 13 women ranging in age from 56 to 79, had undergone a unilateral TKA at least 12 weeks prior to testing. METHODS: Subjects were first asked to complete an Oxford-12 Questionnaire, which is a self-report assessment of knee-specific functional performance. Height and lower-leg length were then measured. The physical performances tests included the timed-up-and-go test that was used for validation as well as the following tests of interest: 1) foam-stance balance test; 2) repeated sit-to-stand tests with legs straight and rotated; 3) sit-to-stand tests from surfaces at and below lower-leg heights with the TKA leg behind the other; 4) step-up-and-over test with each leg, using both 8-in and 12-in steps; 5) step-up-and-turn test using an 8-in step; 6) squat test; 7) floor transfer test; and 8) the 8-ft walk test. A computerized force platform was used to time selected tests from this battery, while the others were timed with a stopwatch. Each subject performed all randomly ordered physical performance tests while being timed by the investigator. After a short rest period, the subjects performed the test battery one more time. ANALYSES: Test times were inverted so that inability to perform a test could be scored as zero. Model 2 intraclass correlation coefficients (ICC) were calculated to determine test-retest reliability of these performance measures. Correlation coefficients were calculated for each test score and the Oxford-12 and timed-up-and-go scores to assess construct validity of the measures of interest. RESULTS: Test-retest ICC values ranged from 0.66 to 1.00 for the performance tests, with the step-up-and-turn test accounting for the lowest ICC values. Eleven tests were significantly and moderately correlated with the timed-up-and-go measure (r = 0.49 to 0.76) and only three tests were significantly and moderately correlated with the Oxford-12 Questionnaire (r = 0.59 to 0.73). Only 15 subjects were able to answer all Oxford-12 questions. CONCLUSIONS: The Oxford-12 Questionnaire scoring system does not account for "not applicable" responses. The performance tests are reliable and show evidence of moderate construct validity. Therefore, it is appropriate to incorporate some of these measures in functional assessments of patients that have undergone TKA. FUNDING SOURCE: Texas Woman’s University. The authors have no potential for material gain from this study.

Copyright 2004 by the American Physical Therapy Association

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