Reliability of the Foot Function Index: A report of the AOFAS Outcomes Committee

Background: There currently is no widely used, validated, self-administered instrument for measuring musculoskeletal functional status in individuals with nonsystemic foot disorders. The purpose of this paper was to report on the assessment of reliability of one of these instruments. We wanted to determine if the Foot Function Index (FFI), which has been validated in rheumatoid patients without fixed foot deformity or prior foot surgery, would be reliable for a population of patients with foot complaints without systemic disease. Methods: Patients were recruited from five orthopaedic offices where the physicians were members of the American Orthopaedic Foot and Ankle Society. Patients were asked to complete the FFI at the time of their initial office visit and then were given a second copy to complete and return by mail 1 week after their visit. Results: Ninety-six patients completed the first questionnaire, and 54 patients completed the second. Reliability in this population was acceptable with an average of 23.5% of the patients providing retest values within one point of the initial response and an average of 45.3% of the patients providing the same response, for a total of 68.8% of all respondents answering within one point between their initial and second questionnaire. In two of the three categories, there were frequent nonresponses or no applicable responses. Four questions, two in the pain section and two in the activity limitation section, generated 20% or more of the nonapplicable answers. Conclusions: The FFI appears to be a reasonable tool for low functioning individuals with foot disorders. It may not be appropriate for individuals who function at or above the level of independent activities of daily living.