title: Patellofemoral joint forces and stress during forward step-up, lateral step-up, and forward step-down exercises.
abstract: METHODS
  Controlled laboratory study using a repeated-measures design.
  
  
  OBJECTIVE
  To quantify patellofemoral joint reaction force (PFJRF) and stress (PFJS) during forward step-up (FSU), lateral step-up (LSU), and forward step-down (FSD) exercises.
  
  
  BACKGROUND
  Although FSU, LSU, and FSD exercises are commonly used in patellofemoral joint rehabilitation programs, the influence of these stepping tasks on patellofemoral joint kinetics has not been quantified.
  
  
  METHODS
  Three-dimensional lower extremity kinematics and kinetics and electromyographic (EMG) data were obtained from 20 healthy adults during their performance of FSU, LSU, and FSD exercises. The step height for each participant was adjusted to permit a standardized knee flexion angle of 45°. A previously described biomechanical model of the patellofemoral joint was used to quantify PFJRF and PFJS during each task. Peak PFJRF and PFJS during the concentric and eccentric phases of each step task were compared using a 2-factor analysis of variance (ANOVA).
  
  
  RESULTS
  When collapsed across concentric and eccentric phases, peak PFJS was significantly greater during the FSD (mean ± SD, 13.8 ± 0.4 MPa) compared to the LSU (11.5 ± 0.8 MPa; P<.001) and FSU (11.2 ± 0.6 MPa; P = .002) exercises. Peak PFJRF also was significantly greater during the FSD (51.1 ± 2.7 N/kg) compared to the LSU (44.1 ± 3.4 N/kg; P<.001) and FSU (43.6 ± 2.3 N/kg; P = .023) exercises.
  
  
  CONCLUSIONS
  In selecting exercises that promote lower extremity muscle strengthening while minimizing patellofemoral joint loading, LSU and FSU should be considered over FSD exercises, if the same step height is used.
authors.affiliation: Mahidol University, Nakhon Pathom, Thailand.
authors.forename: Chatchada
authors.initials: C
authors.lastname: Chinkulprasert
authors.forename: Roongtiwa
authors.initials: R
authors.lastname: Vachalathiti
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Powers
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D004576:Electromyography; D005081:Exercise Therapy / Q000379:methods; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008297:Male; D057071:Patellofemoral Joint / Q000502:physiology*; D013314:Stress, Mechanical