Relationship Between Lateral Tibial Posterior Slope and Tibiofemoral Kinematics During Simulated Jump Landings in Male Cadaveric Knees.

Background: It is not known mechanistically whether a steeper lateral posterior tibial slope (LTS) leads to an increase in anterior tibial translation (ATT) as well as internal tibial rotation (ITR) during a given jump landing. Hypothesis: A steeper LTS will result in increased ATT and ITR during simulated jump landings when applying knee compression, flexion, and internal tibial torque of increasing severity. Study Design: Descriptive laboratory study. Methods: Seven pairs of cadaveric knees were harvested from young male adult donors (mean ± SD; age, 25.71 ± 5.53 years; weight, 71.51 ± 4.81 kg). The LTS of each knee was measured by a blinded observer from 3-T magnetic resonance images. Two sets of 25 impact trials of ∼700 N (1× body weight [BW] ±10%) followed by 2 sets of 25 trials of 1400 N (2× BW ±10%) were applied to a randomly selected knee of each pair. Similarly, on the contralateral knee, 2 sets of 25 impact trials of ∼1800 N (2.5× BW ±10%) followed by 2 sets of 25 trials of ∼2100 N (3× BW ±10%) were applied. Three-dimensional knee kinematics, including ATT and ITR, were measured at 400 Hz using optoelectronic motion capture. Two-factor linear mixed effect models were used to determine the relationship of LTS to ATT and ITR as impact loading increased. Results: As LTS increased, so did ATT and ITR during increasingly severe landings. LTS had an increasing effect on ATT (coefficient, 0.50; 95% CI, 0.29-0.71) relative to impact force (coefficient, 0.52; 95% CI, 0.50-0.53). ITR was proportional to LTS (coefficient, 1.36; 95% CI, 0.80-1.93) under increasing impact force (coefficient, 0.49; 95% CI, 0.47-0.52). For steeper LTS, the increase in ITR was proportionally greater than the increase in ATT. Conclusion: In male knee specimens, a steeper LTS significantly increased ATT and ITR during jump landings. Clinical Relevance: Increases in ITR and ATT during jump landings lead to increased strain on the anterior cruciate ligament and are therefore associated with greater risk of ligament failure.