• BACKGROUND
    • Inadequate restoration of the knee joint line after total knee arthroplasty may lead to a poor clinical outcome. The purpose of this study was to quantitatively assess the effects of joint line elevation following total knee arthroplasty with increased joint volume on patellofemoral contact kinematics.
  • METHODS
    • Six cadaveric specimens were tested. Patellofemoral contact area, contact pressure, and kinematics were measured following total knee arthroplasty with an anatomic joint line and after 4 and 8mm of joint line elevation, at knee flexion angles of 0°, 30°, 60°, 90° and 120°. Repeated measures analysis of variance with a Tukey post hoc test with a significance level of 0.05 was used for statistical analyses.
  • FINDINGS
    • There was a decrease in contact area with joint line elevation at flexion angles of 60°, 90° and 120° (P=0.009-0.04). There was a significant increase in contact pressure only at 30° of knee flexion with 8mm of joint line elevation (P=0.004). Three of the six specimens showed inferior edge loading of the patella component following 8mm of joint line elevation at 120° of knee flexion. The sagittal plane patellofemoral angle increased significantly with joint line elevation except for 0° knee flexion (P=0.0002-0.02).
  • INTERPRETATION
    • Knee joint line elevation with increased knee volume significantly affects patellofemoral contact area and kinematics and produced inferior edge loading/impingement between the patella and tibial components, this may result in loss of knee range of motion, postoperative pain, and premature component wear.