title: Reduced step length reduces knee joint contact forces during running following anterior cruciate ligament reconstruction but does not alter inter-limb asymmetry.
abstract: BACKGROUND
  Anterior cruciate ligament reconstruction is associated with early onset knee osteoarthritis. Running is a typical activity following this surgery, but elevated knee joint contact forces are thought to contribute to osteoarthritis degenerative processes. It is therefore clinically relevant to identify interventions to reduce contact forces during running among individuals after anterior cruciate ligament reconstruction. The primary purpose of this study was to evaluate the effect of reducing step length during running on patellofemoral and tibiofemoral joint contact forces among people with a history of anterior cruciate ligament reconstruction. Inter limb knee joint contact force differences during running were also examined.
  
  
  METHODS
  18 individuals at an average of 54.8months after unilateral anterior cruciate ligament reconstruction ran in 3 step length conditions (preferred, -5%, -10%). Bilateral patellofemoral, tibiofemoral, and medial tibiofemoral compartment peak force, loading rate, impulse, and impulse per kilometer were evaluated between step length conditions and limbs using separate 2 factor analyses of variance.
  
  
  RESULTS
  Reducing step length 5% decreased patellofemoral, tibiofemoral, and medial tibiofemoral compartment peak force, impulse, and impulse per kilometer bilaterally. A 10% step length reduction further decreased peak forces and force impulses, but did not further reduce force impulses per kilometer. Tibiofemoral joint impulse, impulse per kilometer, and patellofemoral joint loading rate were lower in the previously injured limb compared to the contralateral limb.
  
  
  CONCLUSIONS
  Running with a shorter step length is a feasible clinical intervention to reduce knee joint contact forces during running among people with a history of anterior cruciate ligament reconstruction.
authors.affiliation: Department of Kinesiology, East Carolina University, 332 Ward Sports Medicine Building, Greenville, NC, 27858, United States. Electronic address: Bowersockc14@students.ecu.edu.
authors.forename: Collin D
authors.initials: CD
authors.lastname: Bowersock
authors.affiliation: Department of Physical Therapy, East Carolina University, 2410D Health Sciences Building, Greenville, NC 27834, United States. Electronic address: WillyR@ecu.edu.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Willy
authors.affiliation: Department of Kinesiology, East Carolina University, 332-B Ward Sports Medicine Building, Greenville, NC, 27858, United States. Electronic address: DeVitaP@ecu.edu.
authors.forename: Paul
authors.initials: P
authors.lastname: DeVita
authors.affiliation: Department of Physical Therapy, East Carolina University, 2405A Health Sciences Building, Greenville, NC 27834, United States. Electronic address: WillsonJ@ecu.edu.
authors.forename: John D
authors.initials: JD
authors.lastname: Willson
mesh_terms: D000070598:Anterior Cruciate Ligament Injuries / Q000503:physiopathology / Q000601:surgery*; D059549:Anterior Cruciate Ligament Reconstruction; D001696:Biomechanical Phenomena; D005121:Extremities / Q000502:physiology; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000503:physiopathology; D008297:Male; D020370:Osteoarthritis, Knee / Q000209:etiology; D012307:Risk Factors; D012420:Running / Q000502:physiology*; D013314:Stress, Mechanical; D055815:Young Adult