Early postoperative measures predict 1- and 2-year outcomes after unilateral total knee arthroplasty: importance of contralateral limb strength

Abstract

Background: Total knee arthroplasty (TKA) has been shown to be an effective surgical intervention for people with end-stage knee osteoarthritis. However, recovery of function is variable, and not all people have successful outcomes.

Objective: The aim of this study was to discern which early postoperative functional measures could predict functional ability at 1 year and 2 years after surgery.

Design and methods: One hundred fifty-five people who underwent unilateral TKA participated in the prospective longitudinal study. Functional evaluations were performed at the initial outpatient physical therapy appointment and at 1 and 2 years after surgery. Evaluations consisted of measurements of height, weight, quadriceps muscle strength (force-generating capacity), and knee range of motion; the Timed "Up & Go" Test (TUG); the stair-climbing task (SCT); and the Knee Outcome Survey (KOS) questionnaire. The ability to predict 1- and 2-year outcomes on the basis of early postoperative measures was analyzed with a hierarchical regression. Differences in functional scores were evaluated with a repeated-measures analysis of variance.

Results: The TUG, SCT, and KOS scores at 1 and 2 years showed significant improvements over the scores at the initial evaluation (P<.001). A weaker quadriceps muscle in the limb that did not undergo surgery ("nonoperated limb") was related to poorer 1- and 2-year outcomes even after the influence of the other early postoperative measures was accounted for in the regression. Older participants with higher body masses also had poorer outcomes at 1 and 2 years. Postoperative measures were better predictors of TUG and SCT times than of KOS scores.

Conclusions: Rehabilitation regimens after TKA should include exercises to improve the strength of the nonoperated limb as well as to treat the deficits imposed by the surgery. Emphasis on treating age-related impairments and reducing body mass also might improve long-term outcomes.

Figure 1.

Significant improvements in results of the Timed “Up & Go” Test (TUG) and stair-climbing task (SCT) and in scores on the activities of daily living subset of the Knee Outcome Survey (KOS-ADLS) at 1-year follow-up and 2-year follow-up (asterisk indicates P<.001). Error bars represent 95% confidence intervals.

Figure 2.

Significant relationship between the quadriceps muscle strength of the nonoperated limb at initial evaluation and quantitative functional measures at 1 year. BMI=body mass index, SCT=stair-climbing task, TUG=Timed “Up & Go” Test.

Figure 3.

Significant relationship between the quadriceps muscle strength of the nonoperated limb at initial evaluation and quantitative functional measures at 2 years. BMI=body mass index, SCT=stair-climbing task, TUG=Timed “Up & Go” Test.

Appendix.

Physical Therapy Treatment Regimen–Aggressive Strengthening Protocol ^a Empi, 599 Cardigan Rd, St Paul, MN 55126-4099.

Appendix.

Physical Therapy Treatment Regimen–Aggressive Strengthening Protocol ^a Empi, 599 Cardigan Rd, St Paul, MN 55126-4099.