Ankle sprains are one of the most common soft tissue injuries accounting for nearly 40% of sports injuries. There are large number of procedures for its treatment reported in the literature with largely good results. The ankle forms a functional unit with the subtalar joint. We present a new classification for peritalar lateral instability. There are two intents of this classification. Firstly, the classification demonstrates an assessment and treatment guideline for the many causes of peritalar lateral instability. The second use of the classification is for research purposes so that cohorts of patients can be accurately described and the efficacy of different operations in different groups can be properly assessed. (C) 2014 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.