Test-retest reliability of lower extremity functional and self-reported measures in elderly with osteoarthritis

The aim of this study was to determine the test-retest reliability for a battery of lower limb functional and self-reported health measures [the Short Form 36 (SF-36) and Western Ontario and McMaster University OA Index (WOMAC in elderly with osteoarthritis (OA) of the hip and/or knee. A repeated-measures design was used, in which 21 patients repeated the same tests on two occasions less than 1 week apart. The physical function tests - 8-foot walking distance, stair ascend/descend and right quadriceps strength - demonstrated satisfactory reproducibility with percentage differences on retest ranging from 4% to 7%. The standard error of the measurement (SEM) indicated that these tests demonstrated moderate to good reliability. The hamstring flexor strength measures were unreliable with retest differences of between 16% and 22%. The dimensions of pain and physical function of the WOMAC and six of the eight SF-36 subscales met the standards required for comparing groups of patients. However, the scales measuring role limitation (mental and physical) of the SF-36 showed poor measurement characteristics with a 44% and 201% difference on retest, respectively. The SF-36 physical function and general health subscales together with the pain and physical function dimensions of the WOMAC may be suitable for use as patient self-assessment measures in conjunction with the timed walk and stair test for elderly with lower limb OA.