Increased bone density is not necessarily bone metastasis, which is commonly seen in chronic sclerosing osteomyelitis, bone island, osteoarthritis, compression fracture, ischemia and necrosis of bone tissues, and bone tumor diseases. 1. Chronic sclerosing osteomyelitis: It can be seen in chronic sclerosing osteomyelitis, which can be manifested as abnormal proliferation of bone cortex and increased bone density. 2. Bone island: In cancellous bone, due to the abnormal growth and development of bone, endogenous osteoma, also called bone island, will be produced. It is also called bone island, which is manifested as increased bone density in cancellous bone on the x-ray film. 3. Osteoarthritis: Severe osteoarthritis or osteoarthrosis can be characterized by increased bone density in the subchondral bone. 4. Compression fracture: Compression fracture can also show localized increase in bone density on x-ray because of the dense concentration of bone due to compression. 5. Ischemia and necrosis of bone tissue: when there is ischemia and necrosis of bone tissue, due to the increase of inorganic components in the bone and the decrease of organic components, it can also be manifested as the increase of bone density. 6、It can be seen in some bone tumor diseases: bone metastatic cancer can see the phenomenon of local bone density increase on imaging, and in addition, it can also see the destruction of bone quality and the surrounding soft tissue lesions. Increased bone density is not a unique imaging manifestation of bone metastasis. Therefore, when the signs of increased bone density are found, it is necessary to take into account the condition of the patient and further diagnosis to clarify the cause of increased bone density, and then carry out appropriate treatment according to the specific situation.