Molecular imaging in MSK radiology: Where are we going?

Highlights: • Molecular imaging has an emerging role in the differentiation between active and chronic joint damage in rheumatic disorders. • Molecular imaging provides promising insights for the evaluation of response to therapy in rheumatic disorders. • Molecular imaging of MSK infections overcomes CT and MRI intrinsic limitations, such as in the presence of metal implants. • Further biomedical research on new biomarkers will improve molecular imaging role in the assessment of infectious and inflammatory diseases. Musculoskeletal (MSK) pathologies are one of the leading causes of disability worldwide. However, treatment options and understanding of pathogenetic processes are still partially unclear, mainly due to a limited ability in early disease detection and response to therapy assessment. In this scenario, thanks to a strong technological advancement, structural imaging is currently established as the gold-standard of diagnosis in many MSK disorders but each single diagnostic modality (plain films, high-resolution ultrasound, computed tomography and magnetic resonance) still suffer by a low specificity regarding the characterization of inflammatory processes, the quantification of inflammatory activity levels, and the degree of response to therapy. To overcome these limitations, molecular imaging techniques may play a promising role. Starting from the strengths and weaknesses of structural anatomical imaging, the present narrative review aims to highlight the promising role of molecular imaging in the assessment of non-neoplastic MSK diseases with a special focus on its role to monitor treatment response.