The effect of gender, age, and body mass index on the medial and lateral posterior tibial slopes: a magnetic resonance imaging study

BACKGROUND: The posterior tibial slope (PTS) is crucial in knee joint stability and in maintaining the natural movement of the knee. An increase in the PTS is associated with various knee pathologic conditions, such as anterior cruciate ligament (ACL) injury and anterior tibial translation (ATT). In the present study, we aimed to establish native medial and lateral PTS values for adult Saudis and to identify any association between PTS and gender, age, and body mass index (BMI). MATERIALS AND METHODS: A total of 285 consecutive, normal, magnetic resonance imaging (MRI) studies of the knee were included in the study. The PTS was measured using the proximal anatomical axis of the tibia. The Kruskal-Wallis test was used to compare the medial and lateral PTS angles between age groups. The difference between the medial and lateral posterior tibial slopes was assessed using the Wilcoxon signed-rank test. The Mann-Whitney U test was performed to compare the medial and lateral PTS angles between men and women. Age, gender, and BMI were analyzed by multivariate linear regression to determine whether they positively predict the medial and lateral PTS angles. RESULTS: The mean physiological medial PTS was 5.86 ± 3.0° and 6.61 ± 3.32°, and the lateral PTS was 4.41 ± 3.35° and 4.63 ± 2.85° in men and women, respectively. This difference showed no statistically significant gender dimorphism (p > 0.05). The medial PTS was significantly larger than the lateral PTS (p < 0.0001). There was no statistically significant difference in the medial and lateral PTS angles between age groups (p > 0.05). Higher BMI was significantly associated with a steeper medial PTS (p = 0.001). CONCLUSIONS: This study provided native values for medial and lateral PTS angles in Saudis, which can assist surgeons in maintaining normal knee PTS during surgery. The PTS was not influenced by age. The medial PTS was significantly larger than the lateral PTS in men and women. The PTS showed no significant gender dimorphism. BMI was significantly associated with the medial PTS.