David Levine, PT, PhD, DABPTS (Orthopaedics), CCRP, Cline Chair of Excellence in Physical Therapy and Acting Department Head ,Department of Physical Therapy,The University of Tennessee at Chattanooga, Jim Richards, BEng, MSc, PhD, Professor of Biomechanics, Department of Allied Health Professions, Faculty of Health, University of Central Lancashire, UK and Michael W. Whittle, BSc, MSc, MB, BS, PhD, Formerly Walter M. Cline Jr. Chair of Rehabilitation Technology, The University of Tennessee at Chattanooga, Chattanooga, TN, USA; Director, H. Carey Hanlin Motion Analysis Laboratory, The University of Tennessee at Chattanooga, Chattanooga, TN, USA; Formerly Acting Director, Oxford Orthopaedic Engineering Centre, University of Oxford, Oxford, UK