[Purpose] The purpose of this study was to investigate the factors of ankle instability by using Cumberland ankle instability tool (CAIT), which have been frequently used as ankle instability tools. The participants were divided into the normal ankle group and the instability ankle group. Maximum strength, proprioception, dynamic balance and maximum rage of joint motion were compared in order to find out factors of instability in the questionnaires. [Participants and Methods] A total of 44 participants were classified into the control (CON) group and the chronic ankle instability (CAI) group according to questionnaire types. Muscle strength, proprioception, dynamic balance and maximum joint angle were measured. The independent t-test was used. [Results] In the case of maximum ankle strength, it showed significance in CON group and CAI group ankle dorsiflexion and plantarflexion. In proprioception, it showed significance in CON group and CAI group. In dynamic balance, it showed significance in anterior (ANT) direction of the CON group and CAI group. Maximum joint angle produced significance in dorsiflexion of CON group and CAI group. [Conclusion] Information on maximum strength, proprioception, dynamic balance of anterior direction, and maximum joint angle of dorsiflexion is available through questionnaire CAIT.