title: Electromyographic study of the popliteus muscle in the dynamic stabilization of the posterolateral corner structures of the knee.
abstract: BACKGROUND
  The posterolateral corner of the knee consists of static and dynamic stabilizing structures. Knee injuries often include the posterolateral structures. The popliteus muscle-tendon unit is known as the major dynamic stabilizer of the posterolateral corner.
  
  
  OBJECTIVE
  The dynamic stabilization of the posterolateral structures of the knee via the popliteus muscle-tendon unit during a squatting exercise follows a constant activation pattern.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Within the pilot study, 6 volunteers performed 2 exercises to verify the electrode position scheme and to analyze cross-talk. In the main study 2 static exercises (standing and standing with knees flexed 90°) and 2 dynamic exercises (isolated popliteus muscle activation and squats) were recorded in 17 volunteers. Electromyograms were obtained of the popliteus, medial and lateral gastrocnemius, and quadriceps muscles. Knee angle-related muscle activity was recorded.
  
  
  RESULTS
  In the pilot study it was assumed that the chosen electrode position allowed selective measurement of popliteus muscle activity. In the main study the mean popliteus onset angle was 43° ± 14° of flexion; activity lasted through the reversal point of the squat to 58° ± 21° of flexion during extension movement. Popliteus activity during all testing cycles revealed that the activity in the standing position is the smallest. The highest activity was recorded during the squat and the popliteus muscle-tendon unit exercise.
  
  
  CONCLUSIONS
  This study demonstrates an activation pattern of the popliteus muscle-tendon unit with high interindividual differences in the onset angles. A constant activation during the reversal phase of the squatting exercise could be observed.
  
  
  CONCLUSIONS
  Reconstructive procedures of the posterolateral structures often include reconstruction of the popliteus muscle-tendon unit. Reconstructive procedures are usually done in a static manner, thus not addressing the dynamic stabilizing structure in a true functional way. The findings of the current study may be a useful contribution to the ongoing discussion of this topic.
authors.affiliation: Department of Orthopedic Surgery, Medical University of Vienna, Austria. martina.schinhan@meduniwien.ac.at
authors.forename: Martina
authors.initials: M
authors.lastname: Schinhan
authors.forename: Manfred
authors.initials: M
authors.lastname: Bijak
authors.forename: Ewald
authors.initials: E
authors.lastname: Unger
authors.forename: Thomas
authors.initials: T
authors.lastname: Nau
mesh_terms: D000328:Adult; D004576:Electromyography; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D055815:Young Adult