title: In vivo articular cartilage contact kinematics of the knee: an investigation using dual-orthogonal fluoroscopy and magnetic resonance image-based computer models.
abstract: BACKGROUND
  Quantifying the in vivo cartilage contact mechanics of the knee may improve our understanding of the mechanisms of joint degeneration and may therefore improve the surgical repair of the joint after injury.
  
  
  OBJECTIVE
  To measure tibiofemoral articular cartilage contact kinematics during in vivo knee flexion.
  
  
  METHODS
  Descriptive laboratory study.
  
  
  METHODS
  Orthogonal fluoroscopic images and magnetic resonance image-based computer models were used to measure the motion of the cartilage contact points during a quasi-static lunge in 5 human subjects.
  
  
  RESULTS
  On the tibial plateau, the contact point moved in both the anteroposterior and the mediolateral directions during knee flexion. On the medial tibial plateau, flexion angle did not have a statistically significant effect on the location of the contact points. The total translation of the contact point from full extension to 90 degrees of flexion was less than 1.5 mm in the anteroposterior direction, whereas the translation in the mediolateral direction was more than 5.0 mm. In the anteroposterior direction, the contact points were centered on the medial tibial plateau. On the lateral tibial plateau, there was a statistically significant difference between the location of the contact point at full extension and the locations of the contact points at other flexion angles in the anteroposterior direction. No significant difference was detected between the location of the contact points at other flexion angles. The overall range of contact point motion was about 9.0 mm in the anteroposterior direction and about 4.0 mm in the mediolateral direction. The contact points were primarily on the inner half of the medial and lateral tibial plateaus (the half closest to the tibial spine). The contact points on both femoral condyles were also on the inner half of the condyles (near the condylar notch).
  
  
  CONCLUSIONS
  The tibiofemoral contact points move in 3 dimensions during weightbearing knee flexion. The medial tibiofemoral contact points remained within the central portion of the tibial plateau in the anteroposterior direction. Both the medial and lateral tibiofemoral contact points were located on the inner portions of the tibial plateau and femoral condyles (close to the tibial spine), indicating that the tibial spine may play an important role in knee stability.
  
  
  CONCLUSIONS
  The results of this study may provide important insight as to the mechanisms contributing to the development of osteoarthritis after ligament injuries.
authors.affiliation: Bioengineering Laboratory, Department of Orthopaedic Surgery, Massachusetts General Hospital/Harvard Medical School, Boston, Massachusetts 02114, USA. gli1@partners.org
authors.forename: Guoan
authors.initials: G
authors.lastname: Li
authors.forename: Louis E
authors.initials: LE
authors.lastname: DeFrate
authors.forename: Sang Eun
authors.initials: SE
authors.lastname: Park
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Gill
authors.forename: Harry E
authors.initials: HE
authors.lastname: Rubash
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000502:physiology*; D003198:Computer Simulation; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D007592:Joint Diseases / Q000503:physiopathology*; D007719:Knee Joint / Q000033:anatomy & histology* / Q000502:physiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009068:Movement