This brief report details the first ever instrument-based motion description of an accidental "giving way" episode of the ankle joint incurred by a recreational male athlete (age = 22 years; height = 1.78 m; body mass = 97 kg) with chronic ankle instability whilst he was performing a change of direction task. Five inertial measurement units, as well as a high-speed video camera captured his lower limb kinematics during the performance of a maximum effort Agility T-Test, including his accidental "giving way" episode. This episode was analysed and compared to a previous trial during which no incident occurred. Analysis of the inertial measurement unit data revealed that the "giving way" episode was characterised by plantar flexion of the ankle joint, as well as internal rotation and adduction of the ankle-foot complex, with peak rotational velocities reaching 797°/s, 1088°/s and 1734°/s, respectively. This instrument-based motion description provides a unique insight into the characteristic features of a "giving way" episode experienced by a recreational athlete with chronic ankle instability. These findings could inform the development of rehabilitation programmes and the design of protective equipment for individuals with chronic ankle instability.