The Chitranjan Ranawat Award: The nonoperated knee predicts function 3 years after unilateral total knee arthroplasty

Abstract

The long-term functional abilities of patients after a unilateral total knee arthroplasty (TKA) are influenced by the status of the nonoperated knee at the time of the TKA. We hypothesized that in the 3 years after TKA, the nonoperated limb would become more painful, and the quadriceps muscles would weaken; pain and strength would influence performance on functional testing by 3 years after TKA. Healthy control subjects were tested over the same time interval; we hypothesized the controls would also decline in strength and function over time. Individuals with unilateral knee pain (less than 4/10 on a verbal analog scale) were recruited preoperatively. We tested patients 1, 2, and 3 years after TKA to determine changes in strength, self-report outcome measures, and performance on a stair climbing test and the 6-minute walk test. Control subjects without osteoarthritis were tested twice, 2 years apart. The nonoperated limb of patients with TKA weakened from 1 to 2 years, and further weakened from 2 to 3 years after TKA; by 3 years after TKA, the nonoperated limb was more painful compared to the operated limb. Three years after TKA, nonoperated knee pain contributed 44% of the variability in the 6-minute walk and 33% of the variability in the stair climbing test. Patients with TKA were weaker, slower, and had lower self-report outcome measures compared with control subjects at both time intervals. Control subjects also weakened over time, yet were stable on self-report outcome measures and the 6 minute walk test. Weakening of the quadriceps muscles in all participants represents changes due to ageing; however on average the nonoperated limb weakened over time, possibly representing not only changes resulting from aging, but progression of osteoarthrosis in some patients with unilateral TKA.

Level of evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Fig. 1

Quadriceps strength in patients 1, 2, and 3 years after TKA is shown, compared to healthy controls. The nonoperated limb declined from 1 to 2 years after TKA (*p = 0.005) and further declines from 2 to 3 years after TKA (**p = 0.002). Strength of the controls also declined (***p < 0.001) over the same time period. Abbreviations: BMI = body mass index; N = Newtons.

Fig. 2

Knee pain scores from the Knee Outcomes Survey on the nonoperated and operated knee in patients after TKA and both knees of the control group. A score of 5 represents that pain does not affect activities of daily living; a score of 0 represents the inability to perform the activity due to knee pain. The nonoperated knee of patients 3 years after TKA is more painful than the operated knee (*p < 0.001) and control knees (**p < 0.001).