This paper focuses on an extension of a previous study of ROM estimation based on the use of a wireless sensor node equipped with a tri-axial accelerometer and a tri-axial magnetometer. In the study, a rehabilitation protocol has to be selected prior to the ROM estimation and sensory signals from both sensors were integrated and interpreted by the assistive software. In practice, patients can misunderstand and unintentionally perform another protocol resulting in an inaccurate result. Therefore, automatic protocol detection was developed in order to inform the user if the selected and the performed protocols are mismatched.