title: Relative distribution of quadriceps head anatomical cross-sectional areas and volumes--sensitivity to pain and to training intervention.
abstract: BACKGROUND
  Quadriceps heads are important in biomechanical stabilization and in the pathogenesis osteoarthritis of the knee. This is the first study to explore the relative distribution of quadriceps head anatomical cross-sectional areas (ACSA) and volumes, and their response to pain and to training intervention.
  
  
  METHODS
  The relative proportions of quadriceps heads were determined in 48 Osteoarthritis Initiative participants with unilateral pain (65% women; age 45-78 years). Quadriceps head volumes were also measured in 35 untrained women (45-55 years) before and after 12-week training intervention. Cross-sectional areas of the vastus medialis (VM), inter-medius (VIM), and lateralis (VL), and of the rectus femoris (RF) were determined from axial T1-weighted MR images.
  
  
  RESULTS
  The proportion of the VM on the total quadriceps ACSA increased from proximal to distal. The difference in quadriceps ACSA of painful (vs. pain-free) limbs was -5.4% for the VM (p<0.001), -6.8% for the VL (p<0.01), -2.8% for the VIM (p=0.06), and +3.4% for the RF (p=0.67) but the VM/VL ratio was not significantly altered. The muscle volume increase during training intervention was +4.2% (p<0.05) for VM, +1.3% for VL, +2.0% for VIM (p<0.05) and +1.6% for RF.
  
  
  CONCLUSIONS
  The proportion of quadriceps head relative to total muscle ACSA and volume depends on the anatomical level studied. The results suggest that there may be a differential response of the quadriceps heads to pain-induced atrophy and to training-related hypertrophy. Studies in larger samples are needed to ascertain whether the observed differences in response to pain and training are statistically and clinically significant.
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria.
authors.forename: M
authors.initials: M
authors.lastname: Sattler
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria; Chondrometrics GmbH, Ainring, Germany. Electronic address: torben.dannhauer@pmu.ac.at.
authors.forename: T
authors.initials: T
authors.lastname: Dannhauer
authors.affiliation: Department of Sport Science and Kinesiology, University of Salzburg, Salzburg, Austria.
authors.forename: S
authors.initials: S
authors.lastname: Ring-Dimitriou
authors.affiliation: Department of Cell Biology, University of Salzburg, Salzburg, Austria.
authors.forename: A M
authors.initials: AM
authors.lastname: Sänger
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria; Chondrometrics GmbH, Ainring, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Wirth
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria; Chondrometrics GmbH, Ainring, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Hudelmaier
authors.affiliation: Institute of Anatomy, Paracelsus Medical University, Salzburg, Austria; Chondrometrics GmbH, Ainring, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Eckstein
mesh_terms: D000368:Aged; D019412:Anatomy, Cross-Sectional; D018771:Arthralgia / Q000209:etiology / Q000473:pathology* / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*; D009929:Organ Size; D020370:Osteoarthritis, Knee / Q000150:complications / Q000473:pathology* / Q000534:rehabilitation*; D016896:Treatment Outcome
keywords: MRI; Pain; Quadriceps heads; Training