title: Proximodistal alignment of the canine patella: radiographic evaluation and association with medial and lateral patellar luxation.
abstract: OBJECTIVE
  To evaluate the contribution of proximodistal alignment of the patella to patellar luxation, and to evaluate the structures contributing to proximodistal alignment of the patella relative to the femoral trochlea.
  
  
  METHODS
  Retrospective study using a convenience sample.
  
  
  METHODS
  Medium to giant breed dogs (n=106).
  
  
  METHODS
  Medical records and stifle radiographs of 106 dogs were reviewed. Radiographic measurements evaluated the proximodistal alignment of the patella with respect to the femoral trochlea, distal aspect of the femur, and proximal aspect of the tibia. Measurements were compared between dogs with clinically normal stifles (controls; n=51 dogs, 66 stifles), and dogs with a clinical diagnosis of medial patellar luxation (MPL, n=46 dogs, 65 stifles) or lateral patellar luxation (LPL, n=9 dogs, 11 stifles) using ANOVA.
  
  
  RESULTS
  In dogs with MPL, the ratio of patellar ligament length (PLL) to patellar length (PL) was increased, as was the ratio of the distance from the proximal aspect of the patella to the femoral condyle (A) to PL (P<.0001). Dogs with LPL had a decreased A:PL (P=.003) and an increased ratio of the proximal tibial length (PTL) to distal tibial width (DTW; P=.009).
  
  
  CONCLUSIONS
  MPL is associated with a relatively long patellar ligament and patella alta in medium to giant breed dogs. LPL is associated with a relatively long proximal tibia and patella baja. Values for PLL:PL>2.06 and A:PL>2.03 are suggestive of the presence of patella alta, whereas a value for A:PL<1.92 is suggestive of patella baja.
  
  
  CONCLUSIONS
  Measurements of both PLL:PL and A:PL are recommended in dogs with patellar luxation, and surgical correction should be considered in those with abnormal values.
authors.affiliation: Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois at Urbana-Champaign, IL 61802, USA. mostafa@uiuc.edu
authors.forename: Ayman A
authors.initials: AA
authors.lastname: Mostafa
authors.forename: Dominique J
authors.initials: DJ
authors.lastname: Griffon
authors.forename: Michael W
authors.initials: MW
authors.lastname: Thomas
authors.forename: Peter D
authors.initials: PD
authors.lastname: Constable
mesh_terms: D000818:Animals; D004283:Dog Diseases / Q000000981:diagnostic imaging / Q000473:pathology*; D004285:Dogs / Q000033:anatomy & histology* / Q000293:injuries; D010329:Patella / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000293:injuries; D031222:Patellar Dislocation / Q000000981:diagnostic imaging / Q000473:pathology / Q000662:veterinary*; D011859:Radiography; D012189:Retrospective Studies; D013264:Stifle / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000293:injuries