Weight-bearing MRI of the knee: a review of advantages and limits

Abstract

Standard knee imaging with MRI is usually performed with patient in recumbent position under non-weight-bearing conditions. Recently, magnetic resonance imaging systems to scan the knee joint under weight bearing conditions has been proposed as an approach to improve the clinical utility of musculoskeletal MRI. Imaging under loading can be useful to understand the natural motion behavior of the knee joint and to identify conditions that are challenging to diagnose by using standard position. We reviewed the literature on weight-bearing MR imaging of the knee to describe the current state of use of such MRI technologies, evaluating the advantages and the potential limitations of these technologies.

Keywords: Magnetic Resonance Imaging, weight-bearing MRI, knee pathology.

Figure 1.

Open low-filed scanner for weight-bearing imaging of the knee in standard supine (A) and upright configuration (B), after table tilt of about 82°

Figure 2.

Sagittal MRI images of the knee of a patient with ACL rupture in standard supine (A, B) and weight bearing position (C): we can appreciate the anterior tibial translation (red arrows), as a sign of ACL insufficiency under load condition

Figure 3.

Sagittal and coronal MRI images of the knee in standard supine (A, B) and weight-bearing upright position (C, D). Note how the posterior horn meniscal tear (white circle) becomes more evident under weigh-bearing (black arrow), finding consistent with an unstable tear

Figure 4.

Sagittal and axial MRI images of the knee in standard supine (A, B) and weight-bearing position (C, D) of a patient with a high riding patella and patello-femoral instability. Under loading conditions, we can appreciate increase of the Insall-Salvati index (b/a ratio: 1.3; b’/a’ ratio: 1.6) and lateral patellar subluxation (white arrow)