title: Trochlear dysplasia and patellar instability in patients with Down syndrome.
abstract: OBJECTIVE
  To analyze occurrences of trochlear dysplasia in patients with Down syndrome in the presence and absence of femoropatellar instability.
  
  
  METHODS
  Eleven knees with stable patellae and thirteen with unstable patellae in patients with Down syndrome were compared. Radiographs were produced to evaluate patellar height, trochlear angle and femoropatellar congruence angle.
  
  
  RESULTS
  The prevalence ratio for a high patella between the unstable and the stable patients was 1.01 using the Insall-Salvati index and 0.68 using the Caton-Deschamps index. For an abnormal congruence angle, the prevalence ratio was 2.04. An increased congruence angle was only found in four cases, all presenting instability.
  
  
  CONCLUSIONS
  Trochlear dysplasia was only found in cases of instability. The trochlear groove angle and the femoropatellar congruence angle correlated with the presence of patellar instability.
authors.affiliation: Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Tiago Amaral
authors.initials: TA
authors.lastname: Rebouças Moreira
authors.affiliation: Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Marco Kawamura
authors.initials: MK
authors.lastname: Demange
authors.affiliation: Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Riccardo Gomes
authors.initials: RG
authors.lastname: Gobbi
authors.affiliation: Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Zan
authors.initials: Z
authors.lastname: Mustacchi
authors.affiliation: Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: José Ricardo
authors.initials: JR
authors.lastname: Pécora
authors.affiliation: Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Luis Eduardo
authors.initials: LE
authors.lastname: Passarelli Tírico
authors.affiliation: Institute of Orthopedics and Traumatology, Hospital das Clínicas, School of Medicine, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Gilberto Luis
authors.initials: GL
authors.lastname: Camanho
keywords: Down syndrome; Knee; Patellar dislocation