Ankle Osteoarthritis Scale

Abstract

Although there is a wide array of outcome tools for assessing patients with symptomatic ankle arthritis, no disease-specific instrument for ankle arthritis has been shown to be reliable and valid. The purpose of this study was to develop a simple, reliable, and validated outcome measure for the clinical assessment of ankle osteoarthritis. We modified the Foot Function Index, a visual analog-based scale used to assess rheumatoid foot problems, to measure patient symptoms and functional limitations stemming from osteoarthritis of the ankle joint. Test-retest reliability and criterion and construct validity were determined for the overall Ankle Osteoarthritis Scale and its two subscales (pain and disability). Overall reliability ( r = 0.97; 95% confidence interval [CI], 0.94–0.99), pain subscale reliability ( r = 0.95; 95% CI, 0.90–0.98), and disability subscale reliability ( r = 0.94; 95% CI, 0.88–0.97) were excellent. Criterion validity testing of the instrument with the WOMAC (a disease-specific scale for osteoarthritis) and the SF-36 (a general health survey) showed a high degree of concordance for related subscales. Construct validity using a physical measure of ankle function demonstrated sensitivity of the instrument to the degree of joint dysfunction. Normative data were obtained from 562 individuals who were not patients (264 men and 298 women). The responses were analyzed for trends in gender, body mass index, presence of arthritis, history of fracture in relation to the response levels, and age. A small but statistically significant main effect for gender was found, with women consistently reporting higher pain, disability, and total index scores. Body mass index and arthritis were also found to correlate with response answers across the subscale and total index scores; however, these factors only accounted for 12% of the variation. The Ankle Osteoarthritis Scale is a reliable and valid self-assessment instrument that specifically measures patient symptoms and disabilities related to ankle arthritis.