Radiological assessment of the posterior tibial slope as a risk factor for osteoarthritis of the knee in Indian population

Background: Osteoarthritis (OA) is a chronic degenerative disorder that affects the joints, causing pain and stiffness. Its prevalence in India ranges from 22% to 39%. Considering the increasing life span and the burden it imposes on individuals and society, early detection or prediction of OA in high-risk groups is crucial for implementing preventive measures. Several risk factors, including weight, genetic factors, sex, previous traumas, occupational factors, physical activity, lifestyle, and age, are associated with osteoarthritis. The geometry of the articular surface may also play a significant role, especially in the sagittal plane. The posterior tibial slope (PTS), defined as the posterior inclination of the tibial plateau in relation to its longitudinal axis in the lateral view, is a determinant of altered joint biomechanics. However, there is a lack of studies examining the correlation between the PTS angle and the risk of knee osteoarthritis in the Indian population. This study aims to determine the value of, and confirm the association between changes in posterior tibial slope observed on radiographs and osteoarthritis.
Materials and Methods: After obtaining ethical approval, 153 individuals visiting the outpatient department were selected based on inclusion and exclusion criteria. Demographic parameters such as age, sex, weight, height, co-morbidities, and medications were recorded. Knee examination findings, pain assessment using the Visual Analog Scale (VAS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were documented. Knee joint radiographs, including anteroposterior (AP) and lateral views, were examined for patients with early OA (Kellgren-Lawrence Grade I and II). The posterior tibial slope was measured by determining the angle between the tangent to the tibial plateau and the perpendicular direction to the Tibial Shaft Anatomical Axis (TSAA).
Results: The study included 153 individuals with early osteoarthritic knees (Grade I and II). The mean posterior tibial slope measured in our study was found to be 11.5 with a standard deviation of 1.34. The range of PTS in our study was between 7\(^o\) and 13\(^o\).
Conclusion: Our study reveals that the posterior tibial slope in patients with early osteoarthritis was higher compared to the known normal values in the Indian population, suggesting an increased posterior tibial slope in individuals with osteoarthritic degeneration. Therefore, the posterior tibial slope can be used as a marker for screening osteoarthritis and initiating appropriate early interventions.