1. Department of Orthopedics (Friedrichsheim), University Hospital Frankfurt, Goethe University, 60528 Frankfurt am Main, Germany
2. Medical Park St. Hubertus Klinik, 83707 Bad Wiessee, Germany
3. Department of Sport and Exercise Science, University of Salzburg, 5020 Salzburg, Austria
4. Dr. Rolf M. Schwiete Research Unit for Osteoarthritis, Department of Orthopedics (Friedrichsheim), University Hospital Frankfurt, Goethe University, 60528 Frankfurt am Main, Germany