title: Influence of total knee arthroplasty on patellar kinematics and contact characteristics.
abstract: OBJECTIVE
  Femoro-patellar complications are one of the most common problems after total knee arthroplasty (TKA). TKA components that reduce patellar loads and preserve physiological patellar kinematics should reduce these problems. Therefore, we evaluated the patellar kinematics and the retro-patellar contact characteristics in both the intact knee and in the TKA-knee.
  
  
  METHODS
  Eight Thiel-embalmed cadaver knees were tested first intact and then after TKA using rotating as well as gliding inlay and with additional patellar resurfacing while flexing the knee from 0° to 100°. During the examination quadriceps and hamstring forces were applied.
  
  
  RESULTS
  TKA with additional patellar resurfacing led to an increased retro-patellar pressure, a decreased contact area and an increased lateral movement. Although patellar kinematics could not be changed by using a gliding inlay compared to a rotating inlay, the gliding inlay improved retro-patellar contact characteristics by reducing the pressure and increasing the contact area, especially in higher flexion.
  
  
  CONCLUSIONS
  The increased retro-patellar pressure together with the increased lateral movement of the patella after TKA may be one important cause for anterior knee pain appearing after TKA. In view of the improved retro-patellar contact characteristics using a gliding inlay this inlay should be preferred, providing that the posterior cruciate ligament is intact.
authors.affiliation: Institute of Biomechanics, Trauma Center Murnau, Prof-Küntscher-Str 8, 82418 Murnau, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Kainz
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Reng
authors.forename: Peter
authors.initials: P
authors.lastname: Augat
authors.forename: Simone
authors.initials: S
authors.lastname: Wurm
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007720:Knee Prosthesis; D010329:Patella / Q000503:physiopathology / Q000601:surgery*; D057071:Patellofemoral Joint / Q000503:physiopathology / Q000601:surgery*; D011183:Postoperative Complications; D011312:Pressure; D011474:Prosthesis Design; D013314:Stress, Mechanical; D016474:Weight-Bearing