title: Electromyographic and biomechanic analysis of anterior cruciate ligament deficiency and functional knee bracing.
abstract: OBJECTIVE
  Examine the neuromuscular response to functional knee bracing relative to anterior tibial translations in vivo.
  
  
  METHODS
  During randomised brace conditions, electromyographic data with simultaneous skeletal tibiofemoral kinematics were recorded from four anterior cruciate ligament deficient subjects to investigate the effect of the DonJoy Legend functional brace during activity.
  
  
  BACKGROUND
  Knee braces do not increase knee stability but may influence afferent inputs from proprioception and therefore one might expect changes in muscle firing patterns, amplitude and timing.
  
  
  METHODS
  Hoffman bone pins affixed with markers were implanted into the tibia and femur for kinematic measurement. The EMG data from the rectus femoris, semitendinosus, biceps femoris, and lateral head of the gastrocnemius were integrated for each subject in three separate time periods: 250 ms preceding footstrike and two consecutive 125 ms time intervals following footstrike.
  
  
  RESULTS
  With brace, semitendinosus activity significantly decreased 17% prior to footstrike whereas bicep femoris significantly decreased 44% during A2, (P<0.05). Rectus femoris activity significantly increased 21% in A2 (P<0.05). No consistent reductions in anterior translations were evident.
  
  
  CONCLUSIONS
  Our preliminary findings, based on a limited number of subjects, indicate joint stability may result from proprioceptive feedback rather than the mechanical stabilising effect of the brace. Despite a significant increase in rectus femoris activity upon landing, only one subject demonstrated an increase in anterior tibial drawer.
  
  
  CONCLUSIONS
  Studies have shown functional braces do not mechanically stabilise the anterior cruciate ligament deficient knee. Perhaps bracing alters proprioceptive feedback. It has been shown that bracing the anterior cruciate ligament deficient knee may affect hamstring and quadriceps activity. Our findings stresses the importance of functional knee bracing combined with proprioceptive and muscular coordination training in order to increase joint stability.
authors.affiliation: Department of Orthopaedic Surgery, Karolinska Hospital, Institution for Surgical Sciences, Karolinska Institute, 171 76, Stockholm, Sweden. dan.ramsey@kbh.ki.se
authors.forename: Dan K
authors.initials: DK
authors.lastname: Ramsey
authors.forename: Per F
authors.initials: PF
authors.lastname: Wretenberg
authors.forename: Mario
authors.initials: M
authors.lastname: Lamontagne
authors.forename: Gunnar
authors.initials: G
authors.lastname: Németh
mesh_terms: D000328:Adult; D016118:Anterior Cruciate Ligament / Q000503:physiopathology; D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena; D001915:Braces; D004576:Electromyography; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D007718:Knee Injuries / Q000503:physiopathology* / Q000534:rehabilitation*; D007719:Knee Joint / Q000503:physiopathology*; D008124:Locomotion; D008297:Male; D018482:Muscle, Skeletal / Q000503:physiopathology*; D011434:Proprioception; D013314:Stress, Mechanical