title: Superolateral Hoffa's fat pad edema: association with patellofemoral maltracking and impingement.
abstract: OBJECTIVE
  Nonelderly patients presenting with knee pain often have patellofemoral maltracking or impingement abnormalities. There is a relative paucity of literature on the incidence and significance of impingement-related edema of the superolateral aspect of Hoffa's (infrapatellar) fat pad in these cases. Our study was designed to systematically evaluate the correlation of superolateral Hoffa's fat pad edema with various anatomic parameters of trochlear morphology and patellar alignment.
  
  
  METHODS
  We evaluated 50 knee MRI examinations in 47 patients for the presence of edema in superolateral Hoffa's fat pad and associated anatomic abnormalities of the patellofemoral joint.
  
  
  RESULTS
  Of the 50 examinations, 25 (50%) showed superolateral Hoffa's fat pad edema, and statistically significant differences were seen between those with and without edema with respect to sex (6/22 men vs 19/28 women) and patellar tendon patellar-length ratio (1.3 ± 0.16 and 1.1 ± 0.12 for those with and without edema, respectively).
  
  
  CONCLUSIONS
  The findings in our study suggest that edema in superolateral Hoffa's fat pad may be an important indicator of underlying patellofemoral maltracking or impingement in younger, symptomatic patients.
authors.affiliation: The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Hospital, 601 N Caroline St., Room 4214, Baltimore, MD 21287, USA. tsubhaw1@jhmi.edu
authors.forename: Ty K
authors.initials: TK
authors.lastname: Subhawong
authors.forename: John
authors.initials: J
authors.lastname: Eng
authors.forename: John A
authors.initials: JA
authors.lastname: Carrino
authors.forename: Avneesh
authors.initials: A
authors.lastname: Chhabra
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D004487:Edema / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007592:Joint Diseases / Q000175:diagnosis*; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged