This issue of PET Clinics is Part I of a two-part issue, and focuses on PET-CT-MRI Applications of Musculoskeletal Disorders. It is edited by Drs. Abass Alavi (the Consulting Editor of PET Clinics), Ali Salavati, Ali Gholamrezanezhad and Ali Guermazi. Articles will include: Basic principles, methodology, and imaging protocol for musculoskeletal applications; Sodium 18F-Fluoride PET-CT-MR of bone and joint disorders; In vivo molecular imaging of inflammation and infection; Radionuclide therapy for osseous metastases; Novel whole-body MR imaging techniques in MSK disorders; MRI of joint infection and inflammation with emphasis on DCE-MRI; Quantitative techniques for musculoskeletal MRI at 7 Tesla; Role of contrast enhanced (including iodine overlay image), spectral, and dual energy CT in MSK applications; Percutaneous thermal ablation in musculoskeletal system: Post-procedural PET-CT imaging; Soft tissue sarcomas of Musculoskeletal Origin; Application of PET/CT, PET/MR on primary bone malignancies; Future perspective of the application of PET-CT-MRI in musculoskeletal disorders, and more!