Despite its impact on the overall outcome and health-related quality of life (HRQOL) after knee surgery, physical activity has not been investigated directly using accelerometry or step monitoring during the first year after total knee arthroplasty (TKA) due to osteoarthritis (OA). Therefore, the present study aimed to evaluate the development of physical activity over 12 months after surgery and its relationship to clinical outcome and HRQOL.
Fifty-three patients scheduled for primary TKA due to OA were measured with the DynaPort ADL monitor and a step activity monitor preoperatively and at 2, 6, and 12 months of followup. Clinical outcome and HRQOL were investigated using the American Knee Society Score (KSS) and Short Form 36 (SF-36) health survey.
Physical activity increased significantly within 12 months of followup (from mean ± SD 4,993 ± 2,170 gait cycles preoperatively to 5,932 ± 2,111 gait cycles; P = 0.003). Clinical outcome and HRQOL improved from baseline (mean ± SD KSS 88.9 ± 21.4, mean ± SD SF-36 43.1 ± 18.4) to 12 months of followup (mean ± SD KSS 188.6 ± 10.9; P = 0.001 and mean ± SD SF-36 82.5 ± 15.9; P = 0.001). Physical activity parameters did not correlate with clinical outcome.
TKA offers profound improvements of physical activity for the majority of patients. Despite these improvements and the excellent clinical outcome, most patients do not reach the level of physical activity reported for healthy subjects. The activity level after treatment seems to be influenced by physical activity behavior prior to surgery rather than by the treatment itself.