1. Physiology, Biophysics, and Systems Biology Program, Weill Cornell Graduate School of Medical Sciences, New York, NY 10065
2. Department of Orthopaedic Surgery, Hospital for Special Surgery, New York, NY 10021
3. Department of Biomechanics, Hospital for Special Surgery, New York, NY 10021
4. Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 East 70th Street, New York, NY 10021 e-mail: