Association of early ambulation with length of stay and costs in total knee arthroplasty: retrospective cohort study.

OBJECTIVE: The objective of this study was to evaluate the association of early ambulation with length of stay, costs, and outcomes in inpatients undergoing total knee arthroplasty.
DESIGN: This is a retrospective study of 1504 patients who underwent total knee arthroplasty between August 2009 and January 2011 in a tertiary teaching hospital. All patients commenced physiotherapy interventions on postoperative day 1. The patients were categorized into an early ambulation group (began ambulating on postoperative day 1; n = 803) or a late ambulation group (began ambulating on postoperative day 2; n = 701). Multivariable regression and propensity score analyses were used to reduce selection biases.
RESULTS: Early ambulation was associated with a statistically significant reduction in the adjusted average length of stay (-0.44 day; P < 0.001) and adjusted average total hospitalization costs (Singapore, -$385; United States, -$315; P < 0.001). Both groups did not differ significantly in the 90-day readmission rate; however, early ambulation was associated with higher odds of achieving at least 90 degrees of knee flexion (adjusted odds ratio, 1.33; P < 0.01) and requiring a walking aid with a smaller base of support (adjusted proportional odds ratio, 1.36; P < 0.001).
CONCLUSIONS: As little as a 1-day difference in the day of first ambulation was associated with a shorter length of stay, lower hospitalization costs, and improved knee function. The results of this study provide the first empirical support for the usefulness of early ambulation after total knee arthroplasty.