title: New insights into anterior cruciate ligament deficiency and reconstruction through the assessment of knee kinematic variability in terms of nonlinear dynamics.
abstract: OBJECTIVE
  Injuries to the anterior cruciate ligament (ACL) occur frequently, particularly in young adult athletes, and represent the majority of the lesions of knee ligaments. Recent investigations suggest that the assessment of kinematic variability using measures of nonlinear dynamics can provide with important insights with respect to physiological and pathological states. The purpose of the present article was to critically review and synthesize the literature addressing ACL deficiency and reconstruction from a nonlinear dynamics standpoint.
  
  
  METHODS
  A literature search was carried out in the main medical databases for studies published between 1990 and 2010.
  
  
  RESULTS
  Seven studies investigated knee kinematic variability in ACL patients. Results provided support for the theory of "optimal movement variability". Practically, loss below optimal variability is associated with a more rigid and very repeatable movement pattern, as observed in the ACL-deficient knee. This is a state of low complexity and high predictability. On the other hand, increase beyond optimal variability is associated with a noisy and irregular movement pattern, as found in the ACL-reconstructed knee, regardless of which type of graft is used. This is a state of low complexity and low predictability. In both cases, the loss of optimal variability and the associated high complexity lead to an incapacity to respond appropriately to the environmental demands, thus providing an explanation for vulnerability to pathological changes following injury.
  
  
  CONCLUSIONS
  Subtle fluctuations that appear in knee kinematic patterns provide invaluable insight into the health of the neuromuscular function after ACL rupture and reconstruction. It is thus critical to explore them in longitudinal studies and utilize nonlinear measures as an important component of post-reconstruction medical assessment.
  
  
  METHODS
  II.
authors: Nebraska Biomechanics Core Facility, University of Nebraska at Omaha, Omaha, NE 68182-0216, USA.
authors: Leslie M
authors: LM
authors: Decker
authors: Constantina
authors: C
authors: Moraiti
authors: Nicholas
authors: N
authors: Stergiou
authors: Anastasios D
authors: AD
authors: Georgoulis
mesh_terms: D016118:Anterior Cruciate Ligament / Q000503:physiopathology* / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D001696:Biomechanical Phenomena; D005684:Gait / Q000502:physiology; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology* / Q000601:surgery; D007719:Knee Joint / Q000503:physiopathology*; D017711:Nonlinear Dynamics