title: Kinematics and knee muscle activation during sit-to-stand movement in women with knee osteoarthritis.
abstract: BACKGROUND
  The 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.
  
  
  METHODS
  Eleven 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.
  
  
  RESULTS
  A 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.
  
  
  CONCLUSIONS
  Results 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.
authors.affiliation: Motor Control and Learning Laboratory, Faculty of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Greece. Electronic address: bouhouras@phed.auth.gr.
authors.forename: Georgios
authors.initials: G
authors.lastname: Bouchouras
authors.affiliation: Laboratory of Neuromechanics, Faculty of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Greece.
authors.forename: Glykeria
authors.initials: G
authors.lastname: Patsika
authors.affiliation: Motor Control and Learning Laboratory, Faculty of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Greece.
authors.forename: Vassilia
authors.initials: V
authors.lastname: Hatzitaki
authors.affiliation: Laboratory of Neuromechanics, Department of Physical Education and Sports Science of Serres, Aristotle University of Thessaloniki, Greece.
authors.forename: Eleftherios
authors.initials: E
authors.lastname: Kellis
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D004576:Electromyography; D005260:Female; D006615:Hip / Q000503:physiopathology; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology*; D035002:Lower Extremity / Q000503:physiopathology; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D016059:Range of Motion, Articular; D060726:Torso / Q000503:physiopathology
keywords: Arthritis; Electromyography; Ground reaction forces; Hamstrings; Quadriceps; Sit to stand