Validity and interobserver reliability of visual observation to assess partial weight-bearing.

OBJECTIVE To determine the validity and interobserver reliability of visual observation to assess partial weight-bearing. DESIGN Validation and interobserver reliability study. SETTING University medical center. PARTICIPANTS Patients (N=10) with a total hip arthroplasty operated 1 to 12 months prior to the study referred by 10 physical therapists (5 experienced and 5 inexperienced in training patients in partial weight-bearing). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES The amount of weight-bearing assessed by visual estimation (visual analog scale score) in percentage body weight (BW). Actual weight-bearing (percentage BW) as measured with the Pedar Mobile system. The mean difference (systematic error) between visual estimation and the Pedar system and the SD of the differences (random error) were determined by the limits of agreement (LOA) method with multiple observations per subject. The intraclass correlation coefficient (ICC) was calculated as a measure for the interobserver reliability. RESULTS The mean difference +/- SD between visual observation and the reference method was -9.5+/-20.1 percentage BW (95% confidence interval, -24.0 to 5.0 percentage BW) with LOA ranging from -49.8 to 30.8 percentage BW. The ICC was .57. The therapists' experience in partial weight-bearing training had no effect on the mean difference (P=.349) between the 2 methods. CONCLUSIONS Visual observation is not a valid and reliable method to assess partial weight-bearing.