Criterion-related validity of the figure-of-eight method of measuring ankle edema

Study Design: Single-session, prospective, repeated-measures design. Objective: To determine intratester reliability and criterion-related validity of the figure-of-eight method of measuring ankle edema. Background: The measurement of edema is often necessary when physical therapists assess patients with ankle injuries. The figure-of-eight method has been shown to be a reliable method in measuring the size of ankles in subjects without edema but not in subjects with ankle swelling. The validity of this method of measurement has not been established. Methods and Measures: The subjects (mean age, 22.7 +/- 4.4 years) were 7 men and 8 women with observable ankle edema secondary to acute or chronic ankle sprains or injury to the lower extremity. Three figure-of-eight measurements were taken by one tester. These measurements were correlated to measurements taken by another tester using a foot volumeter. Results: The intraclass correlation coefficient (ICC [2,1]) for the figure-of-eight measurements was 0.99. The Pearson Product Moment correlation coefficients between the figure-of-eight measurements and the first volumetric measurement were 0.89 (first figure-of-eight), 0.88 (second figure-of-eight), 0.91 (third figure-of-eight), and 0.90 (mean of all 3 figure-of-eight measurements). Conclusion: The figure-of-eight method was demonstrated to be a reliable and valid indirect method of measuring ankle edema in individuals with edema secondary to sprains or other lower-extremity musculoskeletal disorders.