1. Department of Rehabilitation; Radboudumc University Medical Center; Rehabilitation 901; P.O. Box 9101; Nijmegen 6500 HB The Netherlands
2. Department of Surgery; Radboudumc University Medical Center; Nijmegen The Netherlands
3. Orthopaedic Research Laboratory; Radboud Institute for Health Sciences, Radboud University Medical Center; Nijmegen The Netherlands
4. Laboratory for Biomechanical Engineering; University of Twente; Enschede The Netherlands