1. Menlo Sports Medicine, Menlo Park, California.
2. Department of Orthopaedic Surgery, Stanford University Medical Center, Stanford, California.
3. Bone and Joint R&D Center, Palo Alto Veterans Affairs Health Care Center, Palo Alto, California.
4. Department of Mechanical Engineering, Stanford University, Stanford, California.
5. Department of Biomedical Engineering, Columbia University, New York, New York.