title: Inferior patellar pole fragmentation in children: just a normal variant?
abstract: BACKGROUND
  Fragmentary ossification of the inferior patella is often dismissed as a normal variant in children younger than 10 years of age.
  
  
  OBJECTIVE
  The purpose of this study was to determine whether fragmentary inferior patellar pole ossification is a normal variant or is associated with symptoms or signs of pathology using MRI and clinical exam findings as reference.
  
  
  METHODS
  A retrospective review was performed on 150 patients ages 5-10 years who underwent 164 knee radiography and MRI exams (45.1% male, mean age: 7.8 years). The presence or absence of inferior patellar pole fragmentation on radiography was correlated with the presence or absence of edema-like signal on MR images. Clinical notes were reviewed for the presence of symptoms or signs referable to the inferior patellar pole. These data were compared with a 1:1 age- and sex-matched control group without inferior pole fragmentation. Statistical analysis was performed using two-tailed t-tests.
  
  
  RESULTS
  Forty of 164 (24.4%) knee radiographs showed fragmentary ossification of the inferior patella. Of these 40 knees, 62.5% (25/40) had edema-like signal of the inferior patellar bone marrow compared with 7.5% (3/40) of controls (P = 0.035). Patients with fragmentary ossification at the inferior patella had a significantly higher incidence of documented focal inferior patellar pain compared with controls (20% vs. 2.5%, P = 0.015).
  
  
  CONCLUSIONS
  Inferior patellar pole fragmentation in children 5 to 10 years of age may be associated with localized symptoms and bone marrow edema-like signal and should not be routinely dismissed as a normal variant of ossification.
authors.affiliation: E.B. Singleton Pediatric Radiology, Texas Children's Hospital, 6701 Fannin Street, Suite 470, Houston, TX, 77030-2399, USA.
authors.forename: J Herman
authors.initials: JH
authors.lastname: Kan
authors.forename: Esben S
authors.initials: ES
authors.lastname: Vogelius
authors.forename: Robert C
authors.initials: RC
authors.lastname: Orth
authors.forename: R Paul
authors.initials: RP
authors.lastname: Guillerman
authors.forename: Siddharth P
authors.initials: SP
authors.lastname: Jadhav
mesh_terms: D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D009999:Ossification, Heterotopic / Q000175:diagnosis*; D010329:Patella / Q000473:pathology*; D012189:Retrospective Studies