Abstract: ObjectiveTo compare the coordination characteristic of the vastus medialis (VM), rectus femoris (RF) and vastus lateralis (VL) between patients with knee osteoarthritis and healthy subjects. Methods34 patients with knee osteoarthritis and 34 controls with normal knee were tested in isometric knee extension at knee joint angles of 10°, 60°, 100° flexion and isokinetic knee extension at velocities of 60°/s and 180°/s. Surface electromyogram (EMG) was recorded in the VM, RF and VL. The activation sequence of muscles and VM/VL EMG ratio were analyzed. ResultsThe VM started significantly later than the VL in isokinetic contraction at 180°/s in patients compared with the controls (P<0.05), and the VM/VL EMG ratio decreased in isometric contraction with knee extension at 10° (P<0.05). ConclusionThe coordination of the vastus medialis, rectus femoris and vastus lateralis decreases in the knee osteoarthritis patients.

Key words: knee osteoarthritis, quadriceps femoris, surface electromyogram, muscle strength