PET has traditionally been under-utilized in musculoskeletal imaging for a few reasons, including the excellent performance of musculoskeletal MRI, limited spatial resolution of PET, and lack of reimbursement for such studies. However, with improvements in PET/CT and PET/MRI over the last decade, as well as increased understanding of the pathophysiology of musculoskeletal diseases, there is an emerging potential for PET as a primary or complementary modality in the management of rheumatologic and orthopedic conditions. The low metabolic activity of osseous and tendinous structures can be both an advantage and a disadvantage for PET/CT evaluation: low physiologic background activity by osseous and tendinous structures results in a higher target-to-background ratio in imaging of their disease processes, which is a major advantage. On the other hand, nonneoplastic noninflammatory disorders of the musculoskeletal system, such as traumatic injuries and tendinous and ligamentous abnormalities, can be metabolically hypoactive, and PET will be less sensitive in their detection. In this review, we discuss the role of PET/CT and PET/MRI in the assessment of nononcologic musculoskeletal disorders, including septic arthritis, osteomyelitis, rheumatoid arthritis (RA) and other inflammatory arthropathies, polymyalgia rheumatica (PMR), and postoperative complications of musculoskeletal procedures. We also review different radiopharmaceuticals that can be used in PET/CT and PET/MRI of nontumoral bone and soft-tissue disorders of extremities. In addition, we present novel and emerging indications for PET in rheumatologic and orthopedic applications.Read More: https://www.ajronline.org/doi/full/10.2214/AJR.17.18523