title: Muscle activation features of the osteoarthritic knee with patellar lateral subluxation.
abstract: OBJECTIVE
  The aim of the study was to compare the muscle activation feature of vastus medialis obliquus (VMO) and vastus lateralis (VL) between the osteoarthritic knee patients with patellar lateral subluxation (Group 1B) and without patellar lateral subluxation (Group 1A).
  
  
  METHODS
  Isokinetic muscle strength of the knee extensor was evaluated using a CYBEX NORM dynamometer with angular velocities of 80, 120 and 240 degrees/second (°/sec) respectively, contraction activities of VMO and VL muscle were recorded with synchronized surface electromyography (sEMG). Age-matched healthy subjects were recruited and served as control group (Group 2). The VMO/VL ratio of EMG between Group 1A, Group 1B and Group 2 were compared.
  
  
  RESULTS
  The peak torque in Group A was 40.7 ± 12.9, in Group B was 39.6 ± 12.9 and in Group C was 60.2 ± 9.5 respectively at 80°/sec angular velocity (p < 0.01). There were no significant difference between Group 1A and Group 1B in the three trial of tested velocities (p > 0.01). The sEMG ratios of VMO/VL of Group 1B calculated at angular velocities of 80/sec was 0.769 ± 0.15, 120°/sec was 0.818 ± 0.22 and 240°/ sec was 0.850 ± 0.22, all those were lower than Group 1A and Group 2 (p<0.01).
  
  
  CONCLUSIONS
  Musculature imbalance of VMO and VL may explain the different muscle activation pattern in osteoarthritic knee patients with and without patellar lateral subluxation.
authors: Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Linkou, Taiwan; School of Medicine, Chang Gung University, Taiwan. Electronic address: fttang1239@gmail.com.
authors: Simon Fuk-Tan
authors: SF
authors: Tang
authors: Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Linkou, Taiwan.
authors: Chih-Kuan
authors: CK
authors: Wu
authors: Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Linkou, Taiwan.
authors: Chien-Hung
authors: CH
authors: Chen
authors: Department of Medicine, Veterans General Hospital, Taipei, Taiwan.
authors: John Tzu-Ning
authors: JT
authors: Chen
authors: Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Linkou, Taiwan.
authors: Alice Chu-Wen
authors: AC
authors: Tang
authors: Department of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Linkou, Taiwan.
authors: Shu-Hsia
authors: SH
authors: Wu
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology*; D031222:Patellar Dislocation / Q000150:complications / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000503:physiopathology*
keywords: Electromyography; Osteoarthritic knee; Patellar lateral subluxation; Vastus lateralis; Vastus medialis obliquus