title: Normal patellofemoral kinematic patterns during daily activities in dogs.
abstract: BACKGROUND
  Patellar abnormalities are a common cause of pain and lameness in dogs; however, in vivo the relative motion between the femur and patella in dogs is not well described. The objective of this study was to define normal in vivo sagittal plane patellofemoral kinematics in three axes of motion using non-invasive methods. We hypothesized patellofemoral alignment in the sagittal plane would tightly correlate with the femorotibial flexion angle. Six healthy dogs without orthopedic disease underwent computed tomography (CT) of their hind limbs to create 3-D models of the patella and femur. Normal stifle joint motion was captured via flat-panel imaging while each dog performed a series of routine activities, including sitting, walking, and trotting. The 3-D models of the patella and femur were digitally superimposed over the radiographic images with shape-matching software and the precise movement of the patella relative to the femur was calculated.
  
  
  RESULTS
  As the femorotibial joint flexed, the patellofemoral joint also flexed and the patella moved caudally and distally within the femoral trochlea during each activity. Patellar flexion and distal translation during walk and sit were linearly coupled with the femorotibial flexion angle. Offset was evident while trotting, where patella poses were significantly different between early and late swing phase (p ≤ 0.003). Patellar flexion ranged from 51 to 6° while trotting. The largest flexion angle (92°) occurred during sit. The patella traversed the entire proximodistal length of the femoral trochlea during these daily activities.
  
  
  CONCLUSIONS
  Using single-plane flat-panel imaging, we demonstrated normal in vivo patellofemoral kinematics is tightly coupled with femorotibial kinematics; however, trot kinematic patterns did not follow the path defined by walking and stand-to-sit motions. Our normal data can be used in future studies to help define patellofemoral joint kinematics in dogs with stifle abnormalities.
authors.affiliation: Comparative Orthopaedics Biomechanics Laboratory, College of Veterinary Medicine, University of Florida, PO Box 100126, 2015 SW 16th Ave, Gainesville, FL, 32610-0126, USA.
authors.forename: Erica J
authors.initials: EJ
authors.lastname: Moore
authors.affiliation: Comparative Orthopaedics Biomechanics Laboratory, College of Veterinary Medicine, University of Florida, PO Box 100126, 2015 SW 16th Ave, Gainesville, FL, 32610-0126, USA. stankim@ufl.edu.
authors.forename: Stanley E
authors.initials: SE
authors.lastname: Kim
authors.affiliation: Comparative Orthopaedics Biomechanics Laboratory, College of Veterinary Medicine, University of Florida, PO Box 100126, 2015 SW 16th Ave, Gainesville, FL, 32610-0126, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Banks
authors.affiliation: Comparative Orthopaedics Biomechanics Laboratory, College of Veterinary Medicine, University of Florida, PO Box 100126, 2015 SW 16th Ave, Gainesville, FL, 32610-0126, USA.
authors.forename: Antonio
authors.initials: A
authors.lastname: Pozzi
authors.affiliation: Comparative Orthopaedics Biomechanics Laboratory, College of Veterinary Medicine, University of Florida, PO Box 100126, 2015 SW 16th Ave, Gainesville, FL, 32610-0126, USA.
authors.forename: Jason D
authors.initials: JD
authors.lastname: Coggeshall
authors.affiliation: Comparative Orthopaedics Biomechanics Laboratory, College of Veterinary Medicine, University of Florida, PO Box 100126, 2015 SW 16th Ave, Gainesville, FL, 32610-0126, USA.
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Jones
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004285:Dogs / Q000033:anatomy & histology*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D021621:Imaging, Three-Dimensional / Q000662:veterinary; D008297:Male; D008953:Models, Anatomic; D010329:Patella / Q000000981:diagnostic imaging*; D011859:Radiography / Q000662:veterinary; D016059:Range of Motion, Articular; D012016:Reference Values; D013264:Stifle / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000662:veterinary
keywords: Dog; Gait analysis; Kinematic; Patellofemoral