Abstract
The primary aim of this study was to investigate whether objective daily physical activity, measured using an activity monitor one year after Total Knee Arthroplasty was different from that measured before surgery.
An activity monitor (activPAL) which records the number of steps in addition to the time spent sitting or lying, standing and ‘stepping’ was used to quantify physical activity. Forty-five patients with osteoarthritis (average 69.8 years old) were assessed an average of 38 days before and 368 days after total knee arthroplasty-before. A group of 40 age matched controls were also recruited. In addition to objective daily physical activity, knee range of motion, pain using the visual analogue score and the Western Ontario McMaster University Osteoarthritis Index (WOMAC 3.1) were also recorded before and after surgery.
Patients reported a significant decrease in pain (54%, p< 0.001) and increase in function (62% p< 0.001) after surgery. However, measures of physical activity showed much smaller improvements which were mostly statistically non-significant. The number of steps taken on one day increased by 19% (from 6438 to 7634 steps, p=0.119) and time spent stepping increased from 7.9% to 8.7% (p=0.27). Only average cadence and estimated energy expenditure were statistically significantly higher after surgery, 8% improvement, p=0.003 and 8% improvement, p=0.026 respectively. Stepwise regression analysis showed that only 11.4% of the improvement in physical activity was due to the decrease in pain.
One year after TKA levels of physical activity were still significantly (p< 0.05) lower than those of a group of age matched controls. In conclusion, other factors not measured in this study are to a large part determining the amount of physical activity in patients after knee surgery. Future studies aiming to identify those factors are warranted.
Correspondence should be addressed to: BASK c/o BOA, at the Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London, WC2A 3PE, England.
