Increased medial posterior tibial slope is associated with medial compartment osteoarthritis of the knee

Abstract Purpose The primary aim was to assess the association between medial posterior tibial slope (MPTS) and medial knee osteoarthritis (OA), hypothesising higher MPTS values in OA knees. The secondary aim was to evaluate the prevalence of increased MPTS (≥ 12°), hypothesising a higher prevalence in the OA group compared with the non‐OA group. Methods Patients were retrospectively identified from an institutional database. The OA group comprised patients with isolated medial knee OA (Kellgren–Lawrence [K/L] grade ≥3), while a non‐OA group (K/L grade 0.050). Mean MPTS was higher in the OA group (7.8° ± 3.5° vs. 6.6° ± 2.4°; p < 0.001), and MPTS ≥ 12° was more frequent in OA knees (13.2% vs. 1.9%; p < 0.001). Each 1° increase in MPTS was associated with higher odds of medial OA (OR 1.14, confidence interval [CI] 1.07–1.20), while MPTS ≥ 12° increased the odds of medial OA 7.9‐fold (OR 7.9, CI 3.07–20.49). ROC analysis showed modest discriminative ability for medial OA (AUC = 0.59; optimal cutoff, 8.6°). Conclusion Increased MPTS was significantly associated with medial knee OA. These findings highlight sagittal tibial geometry as a potentially relevant morphological factor and support further longitudinal investigation. Level of Evidence Level III, diagnostic study.