Radiographic assessment of posterior tibial slope and metaphysio-diaphyseal angle as structural markers of knee osteoarthritis in South Indian adults: A cross-sectional comparative study.

Abstract

BackgroundOsteoarthritis (OA) is a leading cause of chronic pain and disability worldwide, particularly among aging populations. Early identification of structural alterations may enable timely intervention and reduce irreversible joint damage. The posterior tibial slope (PTS) and metaphysio-diaphyseal angle (MDA) have been proposed as radiographic biomarkers of knee OA; however, population-specific data from South India are limited.ObjectivesTo evaluate PTS and MDA as radiological markers of knee osteoarthritis in South Indian adults, compare these parameters between osteoarthritic and non-osteoarthritic knees, assess their interrelationship, and determine their diagnostic performance in predicting OA.MethodsA hospital-based cross-sectional comparative study was conducted among 384 adults aged ≥30 years attending the Orthopaedics Department at Chettinad Hospital & Research Institute, Chennai, between June 2022 and January 2024. Equal numbers of osteoarthritic knees (n = 192) and non-OA controls (n = 192) underwent standardized anteroposterior and lateral knee radiography. PTS and MDA were measured digitally using validated techniques.ResultsMean PTS was significantly higher in osteoarthritic knees compared with controls (15.98 ± 2.18° vs 9.78 ± 2.73°, p < 0.001). Similarly, MDA was significantly elevated in the OA group (24.86 ± 4.13° vs 21.44 ± 4.30°, p < 0.001). A moderate positive correlation was observed between PTS and MDA (r = 0.275, p < 0.001; R² = 0.075). ROC analysis demonstrated excellent discriminative ability for PTS (AUC = 0.963) and moderate discriminative ability for MDA (AUC = 0.717). Female participants constituted 52.5% of the OA group, consistent with established sex-related prevalence patterns.ConclusionPosterior tibial slope and metaphysio-diaphyseal angle are significantly increased in osteoarthritic knees among South Indian adults, with PTS showing superior diagnostic accuracy. These parameters may serve as useful adjunctive radiographic markers for early OA detection and risk stratification. Further longitudinal studies are warranted to establish population-specific predictive thresholds.