1. Center for Rehabilitation Research; School of Allied Health Sciences; Texas Tech University Health Sciences Center; Lubbock TX 79430 USA
2. Department of Community and Family Medicine; Duke University; DUMC 104002 Durham NC 27710 USA
3. Orthopaedic Surgery; DUMC, 3077 Durham NC 27710 USA
4. Duke Orthopedics; DUMC box 2807 Durham NC 27710 USA
5. Department of Physical Therapy; Grand Valley State University; 301 Michigan Street Grand Rapids MI 49503 USA
6. Division of Physical Therapy; Duke University; Durham NC 27710 USA