title: Sagittal plane trunk posture influences patellofemoral joint stress during running.
abstract: METHODS
  Cross-sectional, repeated-measures. Objectives To examine the association between sagittal plane trunk posture and patellofemoral joint (PFJ) stress, and to determine whether modifying sagittal plane trunk posture influences PFJ stress during running.
  
  
  BACKGROUND
  Patellofemoral pain is the most common injury among runners and is thought to be the result of elevated PFJ stress. While sagittal plane trunk posture has been shown to influence tibiofemoral joint mechanics, no study has examined the influence of trunk posture on PFJ kinetics.
  
  
  METHODS
  Twenty-four asymptomatic recreational runners (12 women, 12 men) ran overground at a speed of 3.4 m/s under 3 trunk-posture conditions: self-selected, flexed, and extended. Trunk and knee kinematics, ground reaction forces, and electromyographic signals from selected lower extremity muscles were obtained. A previously described PFJ biomechanical model was used to quantify PFJ stress.
  
  
  RESULTS
  The mean ± SD trunk flexion angles under the self-selected, flexed, and extended running conditions were 7.3° ± 3.6°, 14.1° ± 4.8°, and 4.0° ± 3.9°, respectively. A significant inverse relationship was observed between mean trunk flexion angle and peak PFJ stress during the self-selected condition (r = -0.60, P = .002). Peak PFJ stress was significantly lower in the flexed condition (mean ± SD, 20.2 ± 3.4 MPa; P<.001) and significantly higher in the extended condition (23.1 ± 3.4 MPa; P<.001) compared to the self-selected condition (21.5 ± 3.2 MPa).
  
  
  CONCLUSIONS
  Sagittal plane trunk posture has a significant influence on PFJ kinetics during running. Incorporation of a forward trunk lean may be an effective strategy to reduce PFJ stress during running.
authors.affiliation: Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, CA.
authors.forename: Hsiang-Ling
authors.initials: HL
authors.lastname: Teng
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Powers
mesh_terms: D000293:Adolescent; D000328:Adult; D018771:Arthralgia / Q000209:etiology / Q000503:physiopathology; D001696:Biomechanical Phenomena; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D057071:Patellofemoral Joint / Q000293:injuries / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D012307:Risk Factors; D012420:Running / Q000293:injuries / Q000502:physiology*; D013314:Stress, Mechanical; D060726:Torso / Q000502:physiology*; D055815:Young Adult
keywords: anterior knee pain; chondromalacia; patella