How Active Are Our Patients in the First 6 Weeks Following Total Knee Arthroplasty?

Background: Patient activity after total knee arthroplasty (TKA) surgery has been estimated through patient-reported outcome measures. The use of data from an implanted sensor that transmits daily gait activity provides a more objective, complete recovery trajectory.

Methods: In this retrospective analysis of 794 patients who received a TKA with sensors in the tibial extension between October 4, 2021, and January 13, 2023, the average age of the patients was 64 years, and the cohort was 54.9% women. During the 6-week postoperative period, 90.3% of patients transmitted data. Patient activity in terms of qualified step count, cadence, walking speed, stride length, functional tibial range of motion (ROM), and functional knee ROM were compared at 1 week, 3 weeks, and 6 weeks postoperatively.

Results: All gait parameters increased in the first 6 weeks postsurgery: qualified step count increased 733%, cadence increased 22%, walking speed increased 50%, stride length increased 17%, tibial ROM increased 19%, and functional knee ROM increased 14%. There were statistically significant differences at both postoperative periods (P = .029, P < .001, and P < .001 at 3 and 6 weeks, respectively) in step counts for different body mass index (BMI) categories, with qualified step counts decreasing with increasing BMI. Patients under 65 years tended to have a higher qualified step count than those 65 and older at all time points, but these differences were not statistically significant. Men had significantly higher step counts than women (P < .001 at 1, 3, and 6 weeks).

Conclusions: Initial results with an implanted sensor that collects data during activities of daily living confirm that 90% of patients transmit objective gait metrics daily after TKA surgery. Those results differ by sex and BMI.

Level Of Evidence: III Retrospective Cohort Study.