Kinematics and knee muscle activation during sit-to-stand movement in women with knee osteoarthritis

• Women with knee osteoarthritis, rise from the chair using greater knee muscle co-contraction.
• Also, they use earlier and greater activation of the hamstrings.
• The above results in reduced hip and knee range of motion.
• Nevertheless, they perform the movement at the same duration compared to healthy subjects.

BackroundThe purpose of this study was to compare joint kinematics, knee and trunk muscle activation and co-activation patterns during a sit-to-stand movement in women with knee osteoarthritis and age-matched controls.MethodsEleven women with knee osteoarthritis (mean and standard deviation, age: 66.90, 4.51 years, height: 1.63, 0.02 m, mass: 77.63, 5.4 kg) and eleven healthy women (mean and standard deviation, age: 61.90, 3.12 years, height: 1.63 m, 0.03, mass: 78.30, 4.91 kg) performed a Sit to Stand movement at a self-selected slow, normal and fast speed. Three-dimensional joint kinematics of the lower limb, vertical ground reaction forces and electromyographic activity of the biceps femoris vastus lateralis and erectus spinae were recorded bilaterally.FindingsA two-way ANOVA showed that the osteoarhtitis group performed the sit to stand task using a smaller knee and hip range of motion compared with the control group while no differences in temporal kinematics and ground reaction force-related parameters were observed. In addition, women with osteoarhtritis displayed significantly lower vastus lateralis coupled with a higher biceps feomoris electromyographic activity and higher agonist–antagonist co-contraction and co-activation than asymptomatic women. The activation of erectus spinae was not different between groups.InterpretationResults indicate that patients with moderate knee osteoarthritis rise from the chair using greater knee muscle co-contraction, earlier and greater activation of the hamstrings which results in reduced hip and knee range of motion. This may be a way to overcome the pain and potential muscle atrophy of knee extensor muscles without compromising overall task duration.