Correlation between Clinical Tests of Anterior Cruciate Ligament (ACL) Deficiency and Degree of Anteroposterior (AP) Laxity and Rotational

Background: Accurate assessment of both anteroposterior (AP) and rotational instability is essential in the evaluation and management of anterior cruciate ligament (ACL) injuries. While clinical tests provide qualitative information, quantitative assessment of knee laxity remains limited. MRI of the knee combined with the Porto KT knee testing device (PTKD) allows objective measurement of translational and rotational instability. Objectives: To quantitatively assess AP and rotational instability in ACL-deficient knees using MRI knee with PTKD, to evaluate the correlation between AP and rotational instability, and to study the correlation between anterior drawer test (ADT) grading and MRI-derived AP laxity measurements. Materials and Methods: Forty patients aged 20–60 years with clinical suspicion of ACL injury underwent MRI knee with PTKD. Ten patients with isolated ACL sprain were excluded, and 30 patients (20 males, 10 females) with partial or complete ACL tears were included. MRI was performed on 1.5T and 3T systems using standard knee protocols with additional oblique sagittal imaging along the ACL. Quantitative AP and rotational laxity measurements were obtained using PTKD under controlled posterior–anterior stress with the knee positioned at 20° flexion. AP laxity was measured at the lateral tibial plateau (LP), while rotational instability was calculated from the difference in anterior tibial translation between the medial and lateral plateaus under internal rotation. Pearson correlation analysis was performed. Results: Mean PA stress displacement at the neutral lateral plateau (9.54 ± 5.57 mm) was higher than that at the medial plateau (6.62 ± 3.72 mm). The mean AP laxity was 4.66 ± 2.83 mm. A significant moderate-to-strong positive correlation was observed between PA stress neutral lateral plateau displacement and rotational instability (r = 0.5896, p < 0.001). AP laxity also showed a significant positive correlation with rotational instability, though of lesser strength (r = 0.392, p = 0.035). Conclusion: MRI knee with PTKD enables reliable quantitative assessment of both AP and rotational instability in ACL-deficient knees. Lateral tibial plateau displacement under PA stress is a sensitive indicator of rotational instability. MRI with PTKD serves as a valuable adjunct to clinical examination and may aid in surgical decision-making for ACL reconstruction.