Total Knee Replacement

Total knee replacement (TKR) surgery is the only effective treatment for end-stage knee osteoarthritis (OA), and as the numbers of Americans with knee OA climbs, the utilization of TKR is increasing dramatically. The procedure, which involves surgically replacing the degraded surfaces of the knee joint bones with synthetic materials, is performed when non-invasive medical treatments are no longer adequate, leaving the patient with severe pain or loss of function.
Click here for more information about TKR from the American Academy of Orthopaedic Surgeons (AAOS)

It has been estimated that by 2015, there will be 1 million knee replacements performed annually in the United States, and that number is predicted to rise to 3.5 million annually by 2030[1]. Given the high frequency of TKR procedures, it is of vital importance that we understand the full extent of the outcomes likely following TKR so that consumers and clinicians can make informed choices as to who is likely to have the best outcomes following this invasive and potentially life-changing procedure, and what rehabilitation interventions are likely to optimize these outcomes.

ENACT and TKR: Community and Home Participation after Total Knee Replacement
ENACT is engaged in research exploring the relationship between total knee replacement and participation outcomes. This NIDILRR-funded project uses data from the large Multicenter Osteoarthritis Study (MOST) and The Osteoarthritis Initiative (OAI), as well as interviews from local TKR patients.
Click here to learn more about this project

The bulk of past research into TKR outcomes has focused on pain and physical function, such as getting out of a chair or climbing stairs. While TKR surgery is successful for most patients[2], 20-30% of individuals have persistent pain and functional limitations[3]. ENACT researchers predicted that there may also be a proportion of patients with participation restrictions, i.e. difficulty with engagement in home and community activities. Participation outcomes are especially important, as the antithesis of participation- disability- has been associated with morbidity and mortality.[4]

Dr. Jessica Maxwell is spearheading ENACT’s research into participation outcomes following TKR. An early ENACT project showed that over 1/3 of post-TKR subjects had participation restrictions 1-2 years after surgery and that certain subgroups of patients are more at risk for participation restrictions post-TKR[5]. Following the first study, the ENACT team conducted a study using sophisticated design and statistical methods to compare participation post-TKR to patients with knee OA that did not undergo the procedure[6]. An ancillary study interviewed patients with participation restrictions post-KR to more fully understand their perceptions for their difficulties with home and community activities. ENACT’s goal in this research area is to advance the understanding of biomedical, psychological and environmental risk factors of participation restriction after total joint replacement to develop novel interventions that could improve participation outcomes after TKR.


1 Kurtz S, Ong K, Lau E, Mowat F, Halpern M. Projections of primary and revision hip and knee arthroplasty in the United States from 2005 to 2030. J Bone Joint Surg Am. 2007;89(4):780-785.

2Kane R, Saleh KJ, Wilt TJ, Bershadsky B. The functional outcomes of total knee arthroplasty. 2005; 87A:1719-1724.

3Singh JA, O’Byrne M, Harmsen S, Lewallen D. Predictors of moderate–severe functional limitation after primary Total Knee Arthroplasty (TKA): 4701 TKAs at 2-years and 2935 TKAs at 5-years. Osteoarthritis and Cartilage. 2007;18: 515–521.

4Dale, C., Prieto-Merino, D., Kuper, H., Adamson, J., Bowling, A., Ebrahim, S., & Casas, J. P. Modelling the association of disability according to the WHO International Classification of Functioning, Disability and Health (ICF) with mortality in the British Women’s Heart and Health Study. J Epidemiol Community Health. 2012; 66(2), 170-175.

5Maxwell JL, Keysor JJ, Niu J, et al. Participation following knee replacement: the MOST cohort study. Phys Ther. Nov 2013;93(11):1467-1474. doi: 1410.2522/ptj.20130109. Epub Jun 20130127.

6Maxwell JL, Keysor JJ, Niu J, Singh J, Nevitt MC, Frey-Law L, Felson DT The Effect of Knee Replacement on Participation Restriction: The MOST and OAI Studies. APTA Combined Sections Meeting, February 4, 2014. Las Vegas, NV.