Background/Purpose: In 2009 over 620,000 total knee replacement (TKR) surgeries were performed. That number is expected to increase to 3.5 million annually by 2030.  Post-operative functional gain is variable. On average physical activity and functional ability remain diminished one year post TKR when compared to age matched controls. The purpose of this study was to examine the recovery pattern of physical activity from TKR to 6 months post surgery and its relation to the timing of physical therapy (PT) service received.

Methods: Subjects were 179 participants in an NIH funded RCT of telephone support interventions following unilateral, primary TKR. We requested the PT records from the first 102 participants who completed their TKR rehabilitation in outpatient PT and the first 40 participants who completed their PT rehabilitation in homecare and used no outpatient PT services. We received 90 outpatient and 27 homecare PT records.  Participants were asked to wear an accelerometer (Step Activity Monitor™) at the ankle for four consecutive days (2 weekday and 2 weekend) before surgery and at 8 weeks and 6 months after surgery.  Valid wear days required a minimum of 10 hours of wear time.  Time from surgery to discharge from PT was extracted from PT records.

Results: Participants included 68% female, with a mean (SD) age of 65.1 (8.61). Mean (SD) age was 64 (8.4) and 66 (7.7) years for those completing rehabilitation in outpatient and home care respectively. All participants wore the accelerometer preoperatively with a mean of 3.3 days worn. 174, 163 and 168 participants had at least one valid wear day at baseline, 8 weeks and 6 months after surgery respectively. Mean (SD) steps/day were 7472 (3156), 6658 (3074) and 8295 (3531) at baseline, 8 weeks and 6 months respectively (Figure). Average and median (5970) daily step counts at 8 weeks were approximately 1000 steps fewer than preoperative levels. Mean (SD) and median change in daily steps at 6 months were 738 (2591) and 354 respectively. 30% of participants had completed their rehabilitation by 8 weeks post surgery and 40% had completed it by 9 weeks.  All but one participant who completed rehabilitation in home care had completed it by 8 weeks.

Conclusion: Although average physical activity at 8 weeks post TKR as measured by daily step counts was lower than pre-operative levels, almost one-third of patients had stopped receiving post TKR rehabilitation by that time. Increased functional ability and physical activity are frequent goals of TKR surgery. Our data show that many patients discontinue post TKR rehabilitation when their physical activity is still below pre-operative levels. Further research is needed to understand the association between recovery of physical activity and the timing of PT services post TKR.