Decreased posterior tibial slope increases strain in the posterior cruciate ligament following total knee arthroplasty

The purpose of this study was to measure the strain in the posterior cruciate ligament as a function of knee flexion angle and posterior tibial slope following total knee arthroplasty with a posterior cruciate ligament-retaining design. Posterior cruciate ligament strain was measured in seven fresh-frozen cadavers for posterior tibial slopes of 10 degrees, 8 degrees, and 5 degrees. For all three levels of tibial slope tested, strain in the posterior cruciate ligament increased with increasing flexion angle to approximately 100 degrees and then decreased with increasing flexion. The strain measured at 8 degrees posterior tibial slope was greater than that measured at 10 degrees, but the difference was not significant. The strain measured at 5 degrees posterior slope was significantly greater than strain measured at both 8 degrees and 10 degrees. This increased strain may result in altered knee kinematics and reduced range of motion at higher flexion angles.