title: The effect of different quadriceps loading patterns on tibiofemoral joint kinematics and patellofemoral contact pressure during simulated partial weight-bearing knee flexion.
abstract: OBJECTIVE
  The purpose of this in vitro study was to investigate the influence of different quadriceps loading patterns on tibiofemoral joint kinematics and patellofemoral pressure.
  
  
  METHODS
  A dynamic muscle-loaded knee squat was simulated on eight knee specimens with an upright knee simulator while measuring tibiofemoral joint kinematics and patellofemoral pressure distribution. The quadriceps muscle was attached to three actuators simulating the three main extensor muscles, and five different quadriceps loading patterns were tested.
  
  
  RESULTS
  Tibial axial and varus-valgus-rotation are affected most while changing quadriceps loading patterns from lateral to medial. Higher internal tibial rotation is associated with higher medial muscle load compared to the symmetrical loading condition. Contact force, contact area and maximum peak pressure rise with increasing flexion angles. Accentuating the vastus lateralis muscle induces a significant reduction in patellofemoral contact force and a 30% diminished contact area at 90° of flexion.
  
  
  CONCLUSIONS
  Strengthening the vastus medialis muscle leads to increased internal tibial rotation, thus optimizing patella tracking by lowering the Q-angle. In contrast, weakness of the vastus medialis muscle causes decreased tibial internal rotation and is associated with lower patellofemoral contact pressure and contact area. Vastus medialis exercise is advisable to improve patella tracking but may not be recommended in patients with disorders due to increased patellofemoral contact pressure.
authors.affiliation: Department of Orthopaedic Surgery, University Hospital Tübingen, Hoppe-Seyler-Str. 3, 72076 Tübingen, Germany. Markus.Wuenschel@med.uni-tuebingen.de
authors.forename: Markus
authors.initials: M
authors.lastname: Wünschel
authors.forename: Ulf
authors.initials: U
authors.lastname: Leichtle
authors.forename: Christian
authors.initials: C
authors.lastname: Obloh
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Wülker
authors.forename: Otto
authors.initials: O
authors.lastname: Müller
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D007719:Knee Joint / Q000502:physiology*; D007867:Leg Bones / Q000502:physiology*; D008297:Male; D053580:Muscle Strength; D057071:Patellofemoral Joint / Q000502:physiology; D011312:Pressure; D052097:Quadriceps Muscle / Q000502:physiology*; D012399:Rotation; D016474:Weight-Bearing