title: Functional bracing of ACL injuries: current state and future directions.
abstract: OBJECTIVE
  Functional braces are commonly prescribed to treat anterior cruciate ligament (ACL) injury. The results of the existing literature on functional brace use are mixed. The purpose of this study was to evaluate the history and current state of functional ACL bracing and to identify design criteria that could improve upon current bracing technologies.
  
  
  METHODS
  A literature search was performed through the PubMed MEDLINE database in April 2013 for the keywords "anterior cruciate ligament" and "brace". Articles published between January 1, 1980, and April 4, 2013, were retrieved and reviewed. Current functional braces used to treat ACL injury were identified. The function of the native ACL was carefully studied to identify design requirements that could improve upon current bracing technologies.
  
  
  RESULTS
  Biomechanical evaluations of functional brace effects at time zero have been mixed. Functional brace use reportedly does not improve long-term patient outcomes following ACL reconstruction, but has been shown to reduce subsequent injury rates while skiing in both ACL-deficient and reconstructed skiers. In situ force in the ACL varies with flexion angle and activity. Currently, no brace has been designed and validated to replicate the force-flexion behavior of the native ACL.
  
  
  CONCLUSIONS
  Biomechanical and clinical evidence suggests current functional bracing technologies do not sufficiently restore normal biomechanics to the ACL-deficient knee, protect the reconstructed ACL, and improve long-term patient outcomes. Further research into a functional brace designed to apply forces to the knee joint similar in magnitude to the native ACL should be pursued.
  
  
  METHODS
  III.
authors.affiliation: Department of BioMedical Engineering, Steadman Philippon Research Institute (SPRI), 181W. Meadow Drive, Suite 1000, Vail, CO, 81657, USA.
authors.forename: Sean D
authors.initials: SD
authors.lastname: Smith
authors.forename: Robert F
authors.initials: RF
authors.lastname: Laprade
authors.forename: Kyle S
authors.initials: KS
authors.lastname: Jansson
authors.forename: Asbjørn
authors.initials: A
authors.lastname: Arøen
authors.forename: Coen A
authors.initials: CA
authors.lastname: Wijdicks
mesh_terms: D016118:Anterior Cruciate Ligament / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction; D001915:Braces / Q000639:trends*; D006801:Humans; D007718:Knee Injuries / Q000503:physiopathology / Q000534:rehabilitation* / Q000601:surgery; D016059:Range of Motion, Articular