An electrogoniometer is a piece of equipment used to measure a joint angle during dynamic movement. In some cases, it will only measure in one plane of motion, e.g. Flexion/extension of the knee. However, some may measure a certain movement in different planes simultaneously, such as plantarflexion/ dorsiflexion (pointing the toes down then up again), as well as abduction/adduction of the ankle (side to side movement).