title: Magnetic resonance imaging in patellar lateral femoral friction syndrome (PLFFS): prospective case-control study.
abstract: OBJECTIVE
  To describe morphologic abnormalities and signs of patellar lateral femoral friction syndrome (PLFFS) detected by magnetic resonance imaging (MRI).
  
  
  METHODS
  Prospective study of 56 knees (21 patients and 30 controls) studied by 3Tesla MRI. Comparative analysis of clinical data, quantitative and qualitative imaging criteria in a population of patients with anterior knee pain associated with an abnormal MRI signal along the lateral alar folds of the infrapatellar fat pad, a characteristic sign of PLFFS, and a control population with no anterior knee pain or abnormal signal from the infrapatellar fat pad.
  
  
  RESULTS
  Patients with PLFFS have anterior and/or lateral knee pain. Their knee has anatomical predispositions for instability, primarily with patella alta (P<0.0001), patellar tilt more than 13.5° (P<0.0001), a patellar nose length less than 9 mm (P=0.0037), a patellar nose ratio less than 0.25 (P<0.0001), a TT-TG distance more than 10 mm (P<0.0001), and a trochlear prominence more than 4 mm (P=0.0056). In 35% of patients, patellar chondropathy is visible, and 48% of patients have patellar or trochlear subchondral abnormalities.
  
  
  CONCLUSIONS
  Anterior, lateral, and medial knee pain may be related to PLFFS. Anatomical predispositions contributing to instability are found in these patients. There may be associated chondropathies and osteochondropathies.
authors.affiliation: Osteoarticular Imaging Department, CHU Jean-Minjoz, Besançon, France. b-barbier-brion@hotmail.fr
authors.forename: B
authors.initials: B
authors.lastname: Barbier-Brion
authors.forename: J-M
authors.initials: JM
authors.lastname: Lerais
authors.forename: S
authors.initials: S
authors.lastname: Aubry
authors.forename: D
authors.initials: D
authors.lastname: Lepage
authors.forename: C
authors.initials: C
authors.lastname: Vidal
authors.forename: E
authors.initials: E
authors.lastname: Delabrousse
authors.forename: M
authors.initials: M
authors.lastname: Runge
authors.forename: B
authors.initials: B
authors.lastname: Kastler
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D017276:Friction; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D017847:Patellar Ligament / Q000473:pathology*; D057071:Patellofemoral Joint / Q000473:pathology*; D046788:Patellofemoral Pain Syndrome / Q000175:diagnosis*; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology; D055815:Young Adult