Passive Posterior Tibial Subluxation on Routine Knee MRI as a Secondary Sign of PCL Tear

The MRI posterior drawer test to assess posterior cruciate ligament functionality and knee joint laxity

Clinical Magnetic Resonance Imaging (MRI) of joints is limited to mere morphologic evaluation and fails to directly visualize joint or ligament function. In this controlled laboratory study, we show that knee joint functionality may be quantified in situ and as a function of graded posterior cruciate ligament (PCL)-deficiency by combining MRI and standardized loading. 11 human knee joints underwent MRI under standardized posterior loading in the unloaded and loaded (147 N) configurations and in the intact, partially, and completely PCL-injured conditions. For each specimen, configuration, and condition, 3D joint models were implemented to analyse joint kinematics based on 3D Euclidean vectors and their projections on the Cartesian planes. Manual 2D measurements served as reference. With increasing PCL deficiency, vector projections increased significantly in the anteroposterior dimension under loading and manual measurements demonstrated similar patterns of change. Consequently, if combined with advanced image post-processing, stress MRI is a powerful diagnostic adjunct to evaluate ligament functionality and joint laxity in multiple dimensions and may have a role in differentiating PCL injury patterns, therapeutic decision-making, and treatment monitoring.

Clinics in diagnostic imaging (196). Complete PCL tear

A 21-year-old man presented with left knee pain and instability that persisted three months after a road traffic accident. Physical examination revealed a positive posterior drawer test. Anterior drawer and pivot tests were negative. Magnetic resonance imaging of the knee demonstrated a complete tear of the posterior cruciate ligament (PCL). Recognition of the normal and injured appearances of the PCL is useful to aid the reader in the detection and characterisation of PCL injuries. Isolated acute PCL tears are usually managed conservatively. However, an active search for associated injuries is essential, as their presence may upstage the patients for surgical management.

Imaging the Anterior and Posterior Cruciate Ligaments

The anterior and posterior cruciate ligaments are important stabilizers of the knee joint function. Although they are both similar in their native appearance, they possess slightly different properties and complement each other's function. The imaging findings differ between the anterior and posterior cruciate ligaments. While MRI is the main imaging modality, radiographs and CT have a role in pre- and post-operative imaging. The aim of this review is to present pre-and post-operative imaging findings of injured cruciate ligaments. A special emphasis will be placed on the potential pitfalls in cruciate ligament imaging.