title: Risk of Anterior Cruciate Ligament Injury in Athletes on Synthetic Playing Surfaces: A Systematic Review.
abstract: BACKGROUND
  The effect of synthetic playing surfaces on the risk of injury in athletes is frequently debated in the orthopaedic literature. Biomechanical studies have identified increased frictional force at the shoe-surface interface, theoretically increasing the risk of injury relative to natural grass. This increase in frictional force is potentially relevant for the risk of anterior cruciate ligament (ACL) rupture, where noncontact mechanisms are frequent. However, clinical studies examining this issue have shown mixed results.
  
  
  OBJECTIVE
  The purpose of this study was to systematically review the available literature on risk of ACL rupture on natural grass versus artificial turf. We hypothesized that the risk of ACL rupture on synthetic playing surfaces would not be higher than that of natural grass playing surfaces.
  
  
  METHODS
  Systematic review.
  
  
  METHODS
  A systematic keyword search was performed of OVID, EMBASE, the Cochrane Library of Systematic Reviews, and the PROSPERO International Prospective Register of Systematic Reviews. Candidate articles were included if they reported the risk ratio of ACL rupture on natural grass versus synthetic playing surfaces, were of level 3 evidence or better, and included only ACL injuries sustained during organized athletic events. Exclusion criteria included a study with non-field-related sports and the use of historical cohorts for calculating risk ratios.
  
  
  RESULTS
  A total of 10 studies with 963 ACL injuries met criteria for inclusion, all of which reported on soccer and football cohorts. Among these, 4 studies (753 ACL injuries) found an increased risk of ACL injury on artificial playing surfaces. All 4 of these articles were conducted using American football cohorts, and they included both earlier-generation surfaces (AstroTurf) and modern, 3rd-generation surfaces. Only 1 study in football players found a reduced risk of ACL injury on synthetic playing surfaces. No soccer cohort found an increased risk of ACL injury on synthetic surfaces.
  
  
  CONCLUSIONS
  High-quality studies support an increased rate of ACL injury on synthetic playing surfaces in football, but there is no apparent increased risk in soccer. Further study is needed to clarify the reason for this apparent discrepancy.
authors.affiliation: Department of Orthopaedic Surgery, Walter Reed National Military Medical Center, Bethesda, Maryland, USA gcbalazs@gmail.com.
authors.forename: George C
authors.initials: GC
authors.lastname: Balazs
authors.affiliation: Department of Orthopaedic Surgery, Walter Reed National Military Medical Center, Bethesda, Maryland, USA.
authors.forename: Gabriel J
authors.initials: GJ
authors.lastname: Pavey
authors.affiliation: Department of Orthopaedic Surgery, Walter Reed National Military Medical Center, Bethesda, Maryland, USA.
authors.forename: Alaina M
authors.initials: AM
authors.lastname: Brelin
authors.affiliation: Department of Orthopaedic Surgery, Walter Reed National Military Medical Center, Bethesda, Maryland, USA.
authors.forename: Adam
authors.initials: A
authors.lastname: Pickett
authors.affiliation: Naval Health Clinic Annapolis, United States Naval Academy, Annapolis, Maryland, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Keblish
authors.affiliation: Naval Health Clinic Annapolis, United States Naval Academy, Annapolis, Maryland, USA.
authors.forename: John-Paul H
authors.initials: JP
authors.lastname: Rue
mesh_terms: D000070598:Anterior Cruciate Ligament Injuries; D056352:Athletes; D005538:Football / Q000293:injuries; D006801:Humans; D007718:Knee Injuries / Q000453:epidemiology* / Q000209:etiology; D012307:Risk Factors; D012916:Soccer / Q000293:injuries
keywords: anterior cruciate ligament injury; football; injury risk; playing surfaces; soccer