title: Proximo-distal patellar position in three small dog breeds with medial patellar luxation.
abstract: BACKGROUND
  Medial patellar luxation is thought to be associated with a high proximal position of the patella in the trochlear groove.
  
  
  OBJECTIVE
  To determine whether the ratio of patellar ligament length and patellar length (L:P) is influenced by the stifle angle (75°, 96°, 113°, 130°, and 148°) in small dog breeds and to compare the L:P ratio in dogs of three small dog breeds with and without medial patellar luxation.
  
  
  METHODS
  A mediolateral radiograph of the stifle joint was used to measure the L:P ratio in the stifle joints of dogs of three small breeds with and without medial patellar luxation. The L:P ratio was evaluated at five stifle angles (75°, 96°, 113°, 130°, and 148°) in 14 cadavers (26 stifle joints) of small dog breeds in order to identify the best stifle angle to measure the L:P ratio. Then the mean ± SD L:P ratio was calculated for normal stifles and stifles with medial patellar luxation grades 1, 2, and 3 in 194 Pomeranians, 74 Chihuahuas, and 41 Toy or Standard Poodles.
  
  
  RESULTS
  The L:P ratio was the same for all five stifle angles in the cadavers (p = 0.195). It was also not significantly different in the three breeds (p = 0.135), in normal and medial patellar luxation-affected stifles overall (p = 0.354), and in normal and medial patellar luxation-affected joints within each breed (p = 0.19).
  
  
  CONCLUSIONS
  We conclude that a proximo-distal patellar position is not associated with medial patellar luxation in Pomeranians, Chihuahuas, and Toy or Standard Poodles. Thus a longer patellar ligament length does not play a role in the pathophysiology of medial patellar luxation in these small dog breeds.
authors.affiliation: Chalika Wangdee, DVM, MSc., PhD, Department of Veterinary Surgery, Faculty of Veterinary Science, Chulalongkorn University, 39 Henri Dunant Road, Bangkok 10330, Thailand, Phone: +66 2218 9639, Fax: +66 2252 7007, E-mail: c.wangdee@hotmail.com; chalika.w@chula.ac.th.
authors.forename: C
authors.initials: C
authors.lastname: Wangdee
authors.forename: L F H
authors.initials: LF
authors.lastname: Theyse
authors.forename: H A W
authors.initials: HA
authors.lastname: Hazewinkel
mesh_terms: D000818:Animals; D004285:Dogs / Q000033:anatomy & histology / Q000293:injuries*; D005260:Female; D008297:Male; D010329:Patella / Q000000981:diagnostic imaging / Q000473:pathology; D031222:Patellar Dislocation / Q000000981:diagnostic imaging / Q000209:etiology / Q000473:pathology / Q000662:veterinary*; D011859:Radiography; D013045:Species Specificity; D013264:Stifle / Q000000981:diagnostic imaging / Q000293:injuries* / Q000473:pathology
keywords: Medial patellar luxation; patella alta; proximo-distal patellar position; small dog breeds