1. Department of Orthopedics (Friedrichsheim), University Hospital, Goethe University Frankfurt, 60590 Frankfurt am Main, Germany
2. Dr. Rolf M. Schwiete Research Unit for Osteoarthritis, Department of Orthopedics (Friedrichsheim), University Hospital, Goethe University Frankfurt, 60590 Frankfurt am Main, Germany
3. Department of Sports Medicine and Exercise Physiology, Institute of Sports Sciences, Goethe University Frankfurt, 60487 Frankfurt am Main, Germany
4. Institute of Medical Biometry, University Hospital Heidelberg, 69120 Heidelberg, Germany