• 1
    Helmick CG, Felson DT, Lawrence RC, Gabriel S, Hirsch R, Kwoh CK, et al, for the National Arthritis Data Workgroup. Estimates of the prevalence of arthritis and other rheumatic conditions in the United States. Part I. Arthritis Rheum 2008; 58: 1525.
  • 2
    Centers for Disease Control and Prevention. US obesity trends. URL:
  • 3
    US Department of Commerce. Unprecedented global aging examined in new Census Bureau Report commissioned by the National Institute on Aging. US Census Bureau News.
  • 4
    Hootman JM, Helmick CG. Projections of US prevalence of arthritis and associated activity limitations. Arthritis Rheum 2006; 54: 2269.
  • 5
    Cisternas MG, Yelin E, Katz JN, Solomon DH, Wright EA, Losina E. Ambulatory visit utilization in a national, population-based sample of adults with osteoarthritis. Arthritis Rheum 2009; 61: 1694703.
  • 6
    United States Bone and Joint Decade. The burden of musculoskeletal diseases in the United States. Rosemont (IL): American Academy of Orthopaedic Surgeons; 2008.
  • 7
    Felson DT, Lawrence RC, Dieppe PA, Hirsch R, Helmick CG, Jordan JM, et al. Osteoarthritis: new insights. Part 1: the disease and its risk factors. Ann Intern Med 2000; 133: 63546.
  • 8
    Yelin E. Cost of musculoskeletal diseases: impact of work disability and functional decline. J Rheumatol Suppl 2003; 68: 811.
  • 9
    Physical Activity Guidelines Advisory Committee. Physical Activity Guidelines Advisory Committee report, 2008. Washington: Dept. of Health and Human Services; 2008.
  • 10
    Church TS, Earnest CP, Skinner JS, Blair SN. Effects of different doses of physical activity on cardiorespiratory fitness among sedentary, overweight or obese postmenopausal women with elevated blood pressure: a randomized controlled trial. JAMA 2007; 297: 208191.
  • 11
    Murphy MH, Nevill AM, Murtagh EM, Holder RL. The effect of walking on fitness, fatness and resting blood pressure: a meta-analysis of randomised, controlled trials. Prev Med 2007; 44: 37785.
  • 12
    King AC, Oman RF, Brassington GS, Bliwise DL, Haskell WL. Moderate-intensity exercise and self-rated quality of sleep in older adults: a randomized controlled trial. JAMA 1997; 277: 327.
  • 13
    Kesaniemi YK, Danforth E Jr, Jensen MD, Kopelman PG, Lefebvre P, Reeder BA. Dose-response issues concerning physical activity and health: an evidence-based symposium. Med Sci Sports Exerc 2001; 33: S3518.
  • 14
    Brosse AL, Sheets ES, Lett HS, Blumenthal JA. Exercise and the treatment of clinical depression in adults: recent findings and future directions. Sports Med 2002; 32: 74160.
  • 15
    Haskell WL, Lee IM, Pate RR, Powell KE, Blair SN, Franklin BA, et al. Physical activity and public health: updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Med Sci Sports Exerc 2007; 39: 142334.
  • 16
    De Vreede PL, Samson MM, van Meeteren NL, Duursma SA, Verhaar HJ. Functional-task exercise versus resistance strength exercise to improve daily function in older women: a randomized, controlled trial. J Am Geriatr Soc 2005; 53: 210.
  • 17
    Ettinger WH Jr, Burns R, Messier SP, Applegate W, Rejeski WJ, Morgan T, et al. A randomized trial comparing aerobic exercise and resistance exercise with a health education program in older adults with knee osteoarthritis: the Fitness Arthritis and Seniors Trial (FAST). JAMA 1997; 277: 2531.
  • 18
    Penninx BW, Messier SP, Rejeski WJ, Williamson JD, DiBari M, Cavazzini C, et al. Physical exercise and the prevention of disability in activities of daily living in older persons with osteoarthritis. Arch Intern Med 2001; 161: 230916.
  • 19
    Penninx BW, Rejeski WJ, Pandya J, Miller ME, Di Bari M, Applegate WB, et al. Exercise and depressive symptoms: a comparison of aerobic and resistance exercise effects on emotional and physical function in older persons with high and low depressive symptomatology. J Gerontol B Psychol Sci Soc Sci 2002; 57: P12432.
  • 20
    Physical Activity Guidelines Advisory Committee. Physical Activity Guidelines Advisory Committee report, 2008. Part H: Research recommendations. Washington: Dept. of Health and Human Services; 2008.
  • 21
    Centers for Disease Control and Prevention. A national public health agenda for osteoarthritis 2010. Atlanta: Centers for Disease Control and Prevention and the Arthritis Foundation; 2010.
  • 22
    Osteoarthritis Initiative. Public data from the Osteoarthritis Initiative, a knee health study. 2008. URL:
  • 23
    Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis 1957; 16: 494502.
  • 24
    Altman R, Brandt K, Hochberg M, Moskowitz R, Bellamy N, Bloch DA, et al. Design and conduct of clinical trials in patients with osteoarthritis: recommendations from a task force of the Osteoarthritis Research Society: results from a workshop. Osteoarthritis Cartilage 1996; 4: 21743.
  • 25
    Bohannon RW. Population representative gait speed and its determinants. J Geriatr Phys Ther 2008; 31: 4952.
  • 26
    Washburn RA, Smith KW, Jette AM, Janney CA. The Physical Activity Scale for the Elderly (PASE): development and evaluation. J Clin Epidemiol 1993; 46: 15362.
  • 27
    Washburn RA, McAuley E, Katula J, Mihalko SL, Boileau RA. The Physical Activity Scale for the Elderly (PASE): evidence for validity. J Clin Epidemiol 1999; 52: 64351.
  • 28
    Scott E. OAI Version 0.2.1 08/17/2007. Subject characteristics, risk factors. Release comments. San Francisco: Osteoarthritis Initiative Coordinating Center; 2007. p. 2832. Martin KA, Rejeski WJ, Miller ME, James MK, Ettinger WH Jr, Messier SP. Validation of the PASE in older adults with knee pain and physical disability. Med Sci Sports Exerc 1999; 31: 62733.
  • 29
    Martin KA, Rejeski WJ, Miller ME, James MK, Ettinger WH Jr, Messier SP. Validation of the PASE in older adults with knee pain and physical disability. Med Sci Sports Exerc 1999; 31: 62733.
  • 30
    Dinger MK, Oman RF, Taylor EL, Vesely SK, Able J. Stability and convergent validity of the Physical Activity Scale for the Elderly (PASE) 2. J Sports Med Phys Fitness 2004; 44: 18692.
  • 31
    Johansen KL, Painter P, Kent-Braun JA, Ng AV, Carey S, Da Silva M, et al. Validation of questionnaires to estimate physical activity and functioning in end-stage renal disease. Kidney Int 2001; 59: 11217.
  • 32
    Peterfy C, Li J, Zaim S, Duryea J, Lynch J, Miaux Y, et al. Comparison of fixed-flexion positioning with fluoroscopic semi-flexed positioning for quantifying radiographic joint-space width in the knee: test-retest reproducibility. Skeletal Radiol 2003; 32: 12832.
  • 33
    Osteoarthritis Initiative. Radioagraphic procedure manual for OAI protocol: Osteoarthritis Initiative: a knee health study. 2006. URL: Accessed 3/22/2010.
  • 34
    Altman RD, Hochberg M, Murphy WA Jr, Wolfe F, Lequesne M. Atlas of individual radiographic features in osteoarthritis. Osteoarthritis Cartilage 1995; 3 Suppl A: 370.
  • 35
    McGrory BJ, Harris WH. Can the Western Ontario and McMaster Universities (WOMAC) osteoarthritis index be used to evaluate different hip joints in the same patient? J Arthroplasty 1996; 11: 8414.
  • 36
    Katz JN, Chang LC, Sangha O, Fossel AH, Bates DW. Can comorbidity be measured by questionnaire rather than medical record review? Med Care 1996; 34: 7384.
  • 37
    Pandya R, Metz L, Patten SB. Predictive value of the CES-D in detecting depression among candidates for disease-modifying multiple sclerosis treatment. Psychosomatics 2005; 46: 1314.
  • 38
    Manson JE, Greenland P, LaCroix AZ, Stefanick ML, Mouton CP, Oberman A, et al. Walking compared with vigorous exercise for the prevention of cardiovascular events in women. N Engl J Med 2002; 347: 71625.
  • 39
    Hogan JW, Roy J, Korkontzelou C. Handling drop-out in longitudinal studies. Stat Med 2004; 23: 145597.
  • 40
    Robins JM, Rotnitzky A, Zhao LP. Analysis of semiparametric regression models for repeated outcomes in the presence of missing data. J Am Stat Assoc 1995; 90: 10621.
  • 41
    SAS/STAT software: release 9.02. Carey (NC): SAS Institute; 2008.
  • 42
    US Dept. of Transportation, Federal Highway Administration. Manual on uniform traffic control devices for streets and highways. 2003. URL: Accessed 12/11/2009.
  • 43
    Pate RR, Pratt M, Blair SN, Haskell WL, Macera CA, Bouchard C, et al. Physical activity and public health: a recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA 1995; 273: 4027.
  • 44
    Lee IM. Dose-response relation between physical activity and fitness: even a little is good; more is better. JAMA 2007; 297: 21379.
  • 45
    Brown DW, Brown DR, Heath GW, Balluz L, Giles WH, Ford ES, et al. Associations between physical activity dose and health-related quality of life. Med Sci Sports Exerc 2004; 36: 8906.
  • 46
    Bierman AS. Functional status: the six vital sign. J Gen Intern Med 2001; 16: 7856.
  • 47
    Capodaglio P, Capodaglio EM, Ferri A, Scaglioni G, Marchi A, Saibene F. Muscle function and functional ability improves more in community-dwelling older women with a mixed-strength training programme. Age Ageing 2005; 34: 1417.
  • 48
    Keysor JJ. Does late-life physical activity or exercise prevent or minimize disablement? A critical review of the scientific evidence. Am J Prev Med 2003; 25: 12936.
  • 49
    Topp R, Woolley S, Hornyak J III, Khuder S, Kahaleh B. The effect of dynamic versus isometric resistance training on pain and functioning among adults with osteoarthritis of the knee. Arch Phys Med Rehabil 2002; 83: 118795.