title: Quadriceps fat pad signal intensity and enlargement on MRI: prevalence and associated findings.
abstract: OBJECTIVE
  The purpose of this investigation was to characterize the MRI appearance of the quadriceps fat pad and to correlate the findings with other knee abnormalities, anatomic measurements of the extensor mechanism, and findings from history and at physical examination.
  
  
  METHODS
  Ninety-two consecutive knee MRI examinations from 84 patients were retrospectively reviewed by two musculoskeletal radiologists for quadriceps fat pad enlargement and signal intensity. Other data from the retrospective review included infrapatellar and prefemoral fat pad signal intensity, quadriceps and patellar tendon abnormalities, joint effusion, medial plica, chondromalacia, articular muscle thickness, and prepatellar edema. The patellar length, patellar articular length, patellar tendon length, and femoral sulcus angle were measured. MRI reports were reviewed for meniscal and ligament abnormalities. Clinical data were reviewed for findings of anterior knee pain in the history and at physical examination. The chi-square and Student's t tests were used to determine significant associations.
  
  
  RESULTS
  Twelve percent (11/92) of MRI examinations showed quadriceps fat pad mass effect on the suprapatellar recess, which was associated with intermediate or fluid signal intensity of the quadriceps fat pad (chi(2) = 7.19, p = 0.0274) but with no other findings on knee MRI. Anterior knee pain at physical examination was associated with quadriceps fat pad mass effect (chi(2) = 8.76, p = 0.0031), medial collateral ligament abnormality (chi(2) = 4.83, p = 0.0031), and history of anterior knee pain (chi (2) = 22.76, p < 0.0001).
  
  
  CONCLUSIONS
  Enlargement of the quadriceps fat pad on MRI has a prevalence of 12% and is significantly associated with intermediate or fluid signal intensity of the quadriceps fat pad and anterior knee pain.
authors.affiliation: Department of Radiology, University of Michigan, 1500 E Medical Center Drive, TC-2910G, Ann Arbor, MI 48109-0326, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Roth
authors.forename: Jon
authors.initials: J
authors.lastname: Jacobson
authors.forename: David
authors.initials: D
authors.lastname: Jamadar
authors.forename: Elaine
authors.initials: E
authors.lastname: Caoili
authors.forename: Yoav
authors.initials: Y
authors.lastname: Morag
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Housner
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000453:epidemiology / Q000473:pathology; D007717:Knee / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal; D012189:Retrospective Studies