Quadriceps activity and physical activity profiles over long durations in patients with osteoarthritis of the knee and controls

Exercise is recommended as a non-pharmacological, non-invasive intervention for osteoarthritis (OA) of the knee. Physiological data concerning the duration and intensity of muscle activity or physical activity profiles during normal daily activity for this population is lacking. Our aim was to explore this using surface Electromyography (EMG) and accelerometer-based activity monitoring. Thirty-four patients with knee OA, mean (SD) age 63.2 (9.8) years and 30 aged-matched asymptomatic controls 64.1 (10.9) years participated. The duration of recording was similar in knee OA and control groups – median (IRQ range) 12:34 (10:11–14:17) h and 13:10 (12:02–14:56) h, respectively (p = 0.514). VM and VL were quiescent for 81.8 (75.3–91.0) to 89.2 (81.5–94.7)% of the time. VM was active for significantly longer durations than VL in the highest intensity band for those with knee OA (p = 0.00), and for longer durations in those with knee OA compared to controls (p = 0.027). The median (IRQ range) percentage of the total recording time spent in an upright posture was 32.4 (28.3–43.9)% and 38.8 (33.6–45.8)%, and time spent stepping or walking was 12.7 (9.7–16.4)% and 16.0 (11.9–19.6)% for those with knee OA and controls respectively. These novel data may prove useful for designing therapeutic exercise programmes and lifestyle changes for those with knee OA.