title: Three-dimensional in vivo motion analysis of normal knees using single-plane fluoroscopy.
abstract: BACKGROUND
  Analysis of the movement of anatomically defined reference axes at the femoral condyles relative to the tibia is appropriate for evaluating knee kinematics. However, such parameters have been previously employed only in studies utilizing stop-motion techniques. The purpose of this study was to evaluate in vivo dynamic kinematics for full range of motion in normal knees using the three-dimensional to two-dimensional registration technique and to compare them with previously reported normal knee kinematics obtained via stop-motion techniques.
  
  
  METHODS
  Dynamic motion of the right knee was analyzed in 20 healthy volunteers (10 female, 10 male; mean age 37.2 years). Knee motion was observed when subjects squatted from standing with the knee fully extended to maximum flexion. We determined the following parameters: (1) changes to angles of the geometric center axis (GCA) on the tibial axial plane (rotation angle); (2) anteroposterior translations of the medial and lateral ends of the GCA; and (3) motion patterns in each phase during knee flexion.
  
  
  RESULTS
  All subjects exhibited femoral external rotation (26.1°) relative to the tibia throughout knee flexion. The medial femoral condyle demonstrated anterior translation (5.5 mm) from full extension to 100° flexion, and demonstrated posterior translation (3.9 mm) after 100°, while the lateral femoral condyle demonstrated consistent posterior translation (15.6 mm) throughout knee flexion. All subjects showed medial pivot motion from full extension to nearly 120° flexion. From 120° flexion, bicondylar rollback motion was observed.
  
  
  CONCLUSIONS
  Although the behavior of the medial femoral condyle in our analysis differed somewhat from that seen in previous cadaver studies, the results obtained using dynamic analysis were generally equivalent to those obtained in previous studies employing stop-motion techniques. These results provide control data for future dynamic kinematic analyses of pathological knees.
authors: Department of Orthopaedic Surgery, Niigata Medical Center, 3-27-11 Kobari, Nishi-ku, Niigata, Niigata, 950-2022, Japan.
authors: Osamu
authors: O
authors: Tanifuji
authors: Takashi
authors: T
authors: Sato
authors: Koichi
authors: K
authors: Kobayashi
authors: Tomoharu
authors: T
authors: Mochizuki
authors: Yoshio
authors: Y
authors: Koga
authors: Hiroshi
authors: H
authors: Yamagiwa
authors: Go
authors: G
authors: Omori
authors: Naoto
authors: N
authors: Endo
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D005471:Fluoroscopy / Q000379:methods; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D055815:Young Adult