Correlation between Posterior Tibial Slope and Functional Outcome in Postoperative Anterior Cruciate Ligament Patients

BACKGROUND: Anterior cruciate ligament (ACL) injuries cause significant functional impairment, and while surgical reconstruction is the standard of care, outcomes vary. The osseous anatomy of the knee, specifically the posterior tibial slope (PTS), is a key factor influencing knee biomechanics and graft strain. AIM: To evaluate the correlation between PTS and functional outcomes in patients following arthroscopic ACL reconstruction. MATERIALS AND METHODS: This tertiary center-based prospective observational study included 54 patients (mean age - 27.54 ± 6.66 years) aged 18-50 years with confirmed ACL tear postreconstruction. PTS was measured on lateral knee radiographs using posterior tibial cortex and medial tibial plateau lines. Functional outcomes were assessed postoperatively at 3, 6, and 9 months using Tegner-Lysholm and International Knee Documentation Committee (IKDC) scores. RESULTS: Mean PTS was 8.26 ± 1.25°. Functional scores improved progressively over 8 months. Tegner-Lysholm scores improved from 62.96 ± 6.18 (3 months) to 73.36 ± 6.32 (8 months). IKDC scores rose from 48.96 ± 5.02 (3 months) to 59.26 ± 6.29 (9 months). However, PTS showed a consistent, significant negative correlation with both the Tegner-Lysholm (r = -0.55 at 8 months; P < 0.001) and the IKDC (r = -0.51 at 9 months; P < 0.001). Patients with Lysholm score ≥74 had lower PTS (7.67° ± 1.14°) vs. <74 (8.95° ± 1.00°). Patients with PTS ≤8º achieved significantly better functional outcomes (87%) compared to those with PTS >8º (29%) (P < 0.001). CONCLUSION: Higher PTS is significantly associated with inferior early postoperative functional outcomes. Routine assessment of PTS can help identify patients at risk of slower recovery.