35 The EANM practice guideline for Bone Scintigraphy Primary tumours of bone are relatively rare in adults whereas bone metastases of other cancer entities (e.g. breast, prostate, lung, renal cancer, etc.) are very frequent. In prostate cancer, the assessment of bone scans is increasingly standardized by calculation of the bone scan index and reporting of progression according to PCWG-2 criteria [25, 26]. 2. Rheumatology • Chronic inflammatory arthritis, including rheumatoid arthritis, spondyloarthropathies and related disorders (ankylosing spondylitis, psoriatic arthritis, Reiter’s arthritis, SAPHO syndrome [synovitis, acne, pustulosis, hyperostosis, osteitis], chronic recurrent multifocal osteomyelitis), and sacroiliitis [27-29]. • Osteoarthritis of the lumbar facet joints, hip, femoro-tibial and femoro-patellar osteoarthritis, rhizarthrosis, and tarsal osteoarthritis [30, 31]. • Enthesopathies, such as plantar fasciitis, Achilles tendinitis or bursitis. • (Avascular) osteonecrosis, which is most frequently located at the femoral head, femoral condyle, and tibial plateau. • Osteonecrosis of the jaw (ONJ) [32] • Complex regional pain syndrome type I of the hand, hip, knee, and foot. • Tietze’s syndrome (costochondritis) • Polymyositis • Paget’s disease • Langerhans cell histiocytosis (LCH): Single system LCH and multi-system LCH with bone involvement. • Non-Langerhans cell diseases, such as Erdheim–Chester disease, Schnitzler syndrome, and Rosaï Dorfman disease. • Other rare osteo-articular diseases, such as sarcoidosis with bone involvement, mastocytosis, Behçet’s disease, and familial Mediterranean fever. 3. Bone and joint infections [33] • Osteomyelitis acute, subacute, or chronic of bacterial, mycobacterial or fungal origin • Septic arthritis • Spondylodiscitis or spondylitis • Septic loosening or mechanical complication of internal fixation (long bones or spine) or arthroplasty (hip, knee, ankle, or shoulder) • Malignant (necrotising) external otitis The reader is also referred to other relevant EANM consensus documents and guidelines [34, 35]. 2