title: Anterior tibial translation during different isokinetic quadriceps torque in anterior cruciate ligament deficient and nonimpaired individuals.
abstract: METHODS
  Factorial quasi-experimental design.
  
  
  OBJECTIVE
  To quantify the effect of different levels of isokinetic concentric and eccentric knee extensor torques on the anterior tibial translation in subjects with anterior cruciate ligament (ACL) deficiency. Electromyogram (EMG) activity of 4 leg muscles was recorded in order to detect any co-activation of extensors and flexors.
  
  
  BACKGROUND
  The rehabilitation after an ACL injury is of importance for the functional outcome of the patient. In order to construct a rehabilitation program after that injury, it is important to understand the in vivo relationships between muscle force and tibial translation.
  
  
  METHODS
  Twelve patients with unilateral ACL injury and 11 uninjured volunteers performed 36 repetitions of a quadriceps contraction at different isokinetic concentric and eccentric torque levels, on a KinCom machine (60 degrees x s(-1)), with simultaneous recordings of tibial translation (CA-4000) and EMG activity from quadriceps and hamstrings muscles. Tibial translations and EMG levels were normalized to the maximum of each subject.
  
  
  RESULTS
  The individual anterior tibial translation increased with increased quadriceps torque in a similar manner in both quadriceps contraction modes in all legs tested. During concentric mode, translation was similar in all groups, but during eccentric mode, the mean translation was 38% larger in the ACL injured knees. No quadriceps-hamstrings co-activation occurred in any test or group.
  
  
  CONCLUSIONS
  An ACL deficient knee can limit the translation within a normal space during concentric muscle activity but not during eccentric activity. That limitation depends on other mechanisms than hamstrings co-activation.
authors.affiliation: Department of Neuroscience and Locomotion, Faculty of Health Sciences, Linköping University, Sweden. Joanna.Kvist@hul.liu.se
authors.forename: J
authors.initials: J
authors.lastname: Kvist
authors.forename: C
authors.initials: C
authors.lastname: Karlberg
authors.forename: B
authors.initials: B
authors.lastname: Gerdle
authors.forename: J
authors.initials: J
authors.lastname: Gillquist
mesh_terms: D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000473:pathology; D000070598:Anterior Cruciate Ligament Injuries; D001265:Athletic Injuries / Q000473:pathology*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D026741:Physical Therapy Modalities; D013977:Tibia / Q000502:physiology*; D019415:Torque