Magnetic resonance imaging in the evaluation of cruciate ligament disorders of the knee joint: a narrative review

Background Injuries to the cruciate ligaments are a leading cause of knee instability, functional impairment, and post-traumatic osteoarthritis (PTOA). The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are the primary intra-articular stabilisers of the knee, and their disruption is frequently accompanied by concurrent damage to the menisci, articular cartilage, meniscocapsular ramp lesions, and subchondral bone. Magnetic resonance imaging (MRI) has become the cornerstone non-invasive method for evaluating internal derangements of the knee, owing to its exceptional soft-tissue contrast resolution and multiplanar capability. Aim of the work This narrative review aimed to synthesise the published evidence on the role of MRI in cruciate ligament disorders of the knee, with emphasis on diagnostic accuracy, associated intra-articular pathology, advanced quantitative imaging techniques, and the clinical significance of structural abnormalities detected on imaging. Review A structured literature search was performed in PubMed/MEDLINE, Scopus, and Google Scholar using combinations of the terms “knee MRI”, “cruciate ligament injury”, “ACL”, “PCL”, “meniscal tear”, “ramp lesion”, “bone marrow lesion” (BML), “articular cartilage”, and “T1ρ/T2 mapping”. Sixty-five records were initially identified, and thirty-two peer-reviewed articles were retained after duplicate removal, title/abstract screening, and full-text assessment against predefined inclusion and exclusion criteria. Across the included studies, MRI sensitivity and specificity for ACL and PCL tears ranged from 82–98% against arthroscopic reference standards; given substantial heterogeneity in study design, sample size, and imaging protocol, these figures are reported descriptively rather than as a pooled estimate. Posterior horn tears of the medial meniscus were the most common associated injury in ACL-deficient knees, occurring in conjunction with BMLs that were reported in over 90% of acute ACL injuries in the largest cohorts, predominantly at the lateral femoral condyle and posterolateral tibial plateau. Meniscocapsular ramp lesions were identified in a clinically relevant proportion of ACL-injured knees, with reported MRI specificity for their detection generally exceeding sensitivity. Advanced quantitative techniques, including T1ρ and T2 relaxation time mapping, detected early biochemical cartilage changes before any morphological damage was visible on standard sequences, although this evidence currently rests on a small number of studies with limited sample sizes. Conclusions MRI remains the most comprehensive non-invasive tool available for evaluating cruciate ligament disorders of the knee. Its capacity for simultaneous assessment of ligament integrity, meniscal pathology, articular cartilage status, ramp lesions, and bone marrow changes renders it indispensable for surgical planning and long-term outcome prediction. Advanced quantitative MRI sequences show early promise for earlier detection of cartilage degeneration, but their evidence base remains preliminary and warrants further validation before routine incorporation into clinical protocols.