title: Patellofemoral joint contact area is influenced by tibiofemoral rotation alignment in individuals who have patellofemoral pain.
abstract: METHODS
  Observational, cohort study.
  
  
  OBJECTIVE
  To test the hypothesis that patellar alignment and tibiofemoral rotation alignment explain unique portions of variance in patellofemoral joint contact area in individuals with patellofemoral pain (PFP) and in pain-free control subjects.
  
  
  BACKGROUND
  PFP has been proposed to result from increased patellofemoral joint stress due to decreased contact area. Patellar malalignment (lateral displacement and tilt) is believed to be the main contributor to decreased contact area. Recent studies suggest that transverse plane rotation of the femur and/or tibia may also contribute to decreased contact area.
  
  
  METHODS
  Twenty-one subjects with PFP (16 female, 5 male) and 21 pain-free subjects (14 female, 7 male) participated. Subjects underwent magnetic resonance imaging with the knee in full extension and the quadriceps contracted. Measures of patellofemoral joint contact area, lateral patellar displacement, patellar tilt angle, tibiofemoral rotation angle, and patellar width were obtained. Hierarchical multiple regression analyses were performed for each group using contact area as the dependent variable. The order of independent variables was patellar width, patellar tilt angle, and tibiofemoral rotation angle. To avoid multicolinearity, lateral patellar displacement was not included.
  
  
  RESULTS
  In the PFP group, patellar width and tibiofemoral rotation angle explained 46% of the variance in contact area. In pain-free subjects, patellar width was the only predictor of contact area, explaining 31% of its variance. Patellar tilt angle did not predict contact area in either group.
  
  
  CONCLUSIONS
  Addressing factors that control tibiofemoral rotation may be indicated to increase contact area and reduce pain in individuals with PFP. Future studies should investigate the contributions of patellar alignment and tibiofemoral rotation to patellofemoral joint contact area at a variety of knee flexion angles.
authors.affiliation: Department of Physical Therapy, Saint Louis University, St Louis, MO 63104, USA. salsichg@slu.edu
authors.forename: Gretchen B
authors.initials: GB
authors.lastname: Salsich
authors.forename: William H
authors.initials: WH
authors.lastname: Perman
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur; D006801:Humans; D007719:Knee Joint / Q000473:pathology; D008279:Magnetic Resonance Imaging; D008297:Male; D046788:Patellofemoral Pain Syndrome / Q000175:diagnosis / Q000209:etiology / Q000473:pathology*; D011446:Prospective Studies; D012044:Regression Analysis; D012307:Risk Factors; D013977:Tibia