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Editorial for “Device for Assessing Knee Joint Dynamics During MR Imaging”

Editorial for “Device for Assessing Knee Joint Dynamics During MR Imaging” Weight-bearing (or stress) magnetic resonance imaging (MRI) has yet to gain widespread use in the clinical setting, although this is not without documented changes occurring between conventional supine and weight-bearing MRI. For example, studies of lumbar spine soft tissues, particularly ligamentous and disc changes, but also changes in listhesis, demonstrate central canal or neuroforaminal stenosis that worsen with weight-bearing spinal MRI compared to supine. While these changes may potentially represent management altering pathology, combining conventional supine MRI with flexion/extension radiographs along with clinical presentation suffice for surgical decision-making in most clinical settings. In the same context, weight-bearing MRI of the knee has been investigated with some success. Patellofemoral pain syndrome, a common reason for anterior knee pain in young individuals, provides a relevant application for weightbearing MRI as pain typically occurs with weight-bearing activity. Separate weight-bearing MRI studies have uncovered changes in patellar tilt and contact pressure points involving cartilage that otherwise would not be realized with conventional MRI. Despite promising advancements, weight-bearing MRI frequently utilizes low-field strength magnets that suffer from slower image acquisition and lower resolution images. In this issue of JMRI, Jogi et al present the design, safety, and testing of an MRI-compatible device that simulates weight-bearing with 50% of body weight in the supine position, allowing for imaging in high-field strength magnets (1.5 and 3 T). Although other researchers referenced by the authors have reported devices with effective weight-bearing simulation, Jogi et al present a device that is less bulky than prior constructed apparatuses, with less cost (although no data are presented) and reportedly an easier, quicker application to the subject in the scanner. The authors are confident that the ease of setup allows their device to potentially be used in a clinical setting. While the prospect of clinical use is enticing, the adoption of new technology rarely occurs rapidly unless a niche application arises where no other method suffices. Indeed, even the adoption of evidence-based medicine practices can be thwarted by numerous barriers. Despite skepticism toward clinical application, Jogi et al’s device, with its relatively simplistic design and ease of use, may prove useful for researchers, especially when the design can be easily translated into a functional apparatus by others across the globe. In particular, more widespread availability will facilitate a better understanding of cartilage and menisci, the shock absorbers of the knee. Some of this work has already begun. T2 relaxation times differ between weightbearing and non-weight-bearing states in asymptomatic individuals. Additionally, comparing asymptomatic knees and those affected by osteoarthritis (OA), both T2 and T1rho relaxation times showed larger reductions in OA knees, suggesting decreased ability to absorb weight-bearing stress. Low-field strength weight-bearing MRI established dynamic changes of meniscal position and morphology with knee flexion, but the added availability at higher field strengths may lead to further breakthroughs in understanding meniscal pathology using ultra-short time of echo sequences, which can assess “subclinical” pathology in the meniscus. Expanding availability of weight-bearing MRI can also benefit the study of OA. Currently, with no known diseasemodifying therapies, a better understanding of pathogenesis and progression, including whether observed changes are reversible, can only improve the approach to the disease. Weight-bearing MRI may provide insight into the pathogenesis or potentially uncover a viable imaging biomarker, which can be investigated with greater utilization in studies and incorporation into clinical trials and/or OA imaging databases. Jogi et al provide an important step toward expanded availability of weight-bearing knee MRI that may facilitate unforeseen insight into the dynamic workings of cartilage and meniscal pathology and ultimately OA in the future.