title: Vertical patellar position in large-breed dogs with clinically normal stifles and large-breed dogs with medial patellar luxation.
abstract: OBJECTIVE
  To further define vertical patellar position, as measured by the ratio of patellar ligament length to patellar length (L:P), in large-breed dogs with clinically normal stifles and compare that to the L:P of large-breed dogs with medial patellar luxation (MPL).
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  Large-breed dogs (n = 50) with clinically normal stifle joints and 30 large-breed dogs with MPL.
  
  
  METHODS
  Large-breed dogs with clinically normal stifle joints or MPL were identified and divided into groups (NORM and MPL, respectively). L:P values were determined for each dog by 4 observers from single lateral stifle radiographs. L:P was compared between NORM and MPL groups and 95% confidence intervals (CIs) were calculated.
  
  
  RESULTS
  All 4 observers found a significantly higher L:P (more proximally positioned patella) for the MPL group compared with the NORM group. Overall mean (+/-SEM) L:P were: NORM, 1.71+/-0.020 and MPL, 1.87+/-0.025. The 95% CI was determined to be 1.45-1.97 for the NORM group and 1.57-2.17 for the MPL group.
  
  
  CONCLUSIONS
  Large-breed dogs with MPL had a significantly more proximal vertical patellar position compared with large-breed dogs with clinically normal stifles. Large-breed dogs with L:P values >1.97 are considered to have patella alta.
  
  
  CONCLUSIONS
  Proximal displacement of the patella within the femoral trochlear groove may play a role in MPL in large-breed dogs.
authors.affiliation: Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI, USA. johnsonah1@msn.com
authors.forename: Allen L
authors.initials: AL
authors.lastname: Johnson
authors.forename: Kristyn D
authors.initials: KD
authors.lastname: Broaddus
authors.forename: Joe G
authors.initials: JG
authors.lastname: Hauptman
authors.forename: Sarah
authors.initials: S
authors.lastname: Marsh
authors.forename: Jaime
authors.initials: J
authors.lastname: Monsere
authors.forename: Gustavo
authors.initials: G
authors.lastname: Sepulveda
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D016022:Case-Control Studies; D004283:Dog Diseases / Q000473:pathology*; D004285:Dogs / Q000033:anatomy & histology* / Q000293:injuries; D004204:Joint Dislocations / Q000473:pathology / Q000662:veterinary; D015588:Observer Variation; D010329:Patella / Q000033:anatomy & histology* / Q000293:injuries; D011859:Radiography; D012189:Retrospective Studies; D013264:Stifle / Q000033:anatomy & histology* / Q000000981:diagnostic imaging