The reliability and validity of the Figure of 8 Walk test in older people with knee replacement: does the setting have an impact?

Objective To determine the reliability and validity of the Figure of 8 Walk test (F8W) for older people after knee replacement surgery in the home setting. Design Observational repeated measures. Setting A specialist orthopaedic hospital and participants homes. Participants Seventy-four older adults aged over 55 years one year following knee replacement surgery participated in two assessments more than one week apart. Main Outcome Measure The time to complete, steps, boundary limits and smoothness score from the Figure of 8 Walk test (F8W), the time to complete the Timed Up and Go (TUG) test and the time to complete the Timed Walk Test (TWT). Results Overall, on 95% of occasions, the difference between the measurements for intra-rater reliability were within 1.8 second of the two test times. The difference between the measurements for inter-rater reliability were found to be narrower than for intra-rater reliability with scores within 1.2 second overall on 95% of occasions. The time to perform the F8W was highly correlated to the Timed Up and Go (overall sample r = 0.921) and the variability spread within narrow limits (−0.8 to 0.8 z-scores). This was also true for the Timed Walk Test (overall sample r = 0.834) with a narrow limit of variability on almost all of the observations (−1.16 to 1.16 z-scores). Conclusions The F8W test has good reliability and validity when used in either a clinical or home setting for patients around one year following knee replacement surgery.