[1] Univ Delaware, Dept Phys Therapy, 540 S Coll Ave, Newark, DE 19716 USA
[2] Delaware Orthopaed Specialists, Newark, DE USA
[3] Johns Hopkins Bloomberg Sch Publ Hlth, Ctr Aging & Hlth, Baltimore, MD USA
[4] Johns Hopkins Bloomberg Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA
[5] Univ Pittsburgh, Dept Phys Therapy, Pittsburgh, PA USA