Ankle Osteoarthritis Scale emerges as a significant and robust instrument to estimate the impact of pain and dysfunction within people with end-stage ankle arthritis, even after excluding items 7 and 8. This analysis was intended to validate the function of Ankle Osteoarthritis Scale instrument, a prospective comparative study based on a secondary analysis of patients registered for total ankle replacement or ankle arthrodesis in Vancouver, Canada. A total of 88 participants completed the study. Between September 2014 and August 2017, the participants completed the instrument. Controlling for analysis participants underlying level of ankle function, item difficulty and discrimination parameters were estimated using the item response theory. The differential item function was observed for age, sex and operation.

According to the modification indices, item 10, "walking around the house," would better suit the pain domain as compared to the disability domain. A range of discrimination and difficulty was found in the items of pain domain, whereas, items of disability domain showed a range of discrimination with low difficulty. Differential item functioning for age, sex and total ankle replacement or ankle arthrodesis seemed to be ignorable. Overall outcomes illustrate that the Ankle Osteoarthritis Scale appears like an excellent diagnostic tool for end-stage ankle arthritis.