Giant cell tumor of bone, also known as osteoblastoma, is a locally aggressive tumor, usually solitary and mostly benign, but also considered by some to be a potentially malignant tumor. The common clinical manifestations are pain, swelling or lump, joint dysfunction, etc. Some patients are seen for pathological fracture, and are seen with extensive bone destruction. 1.X-ray examination: The lesion mostly shows central or eccentric osteolytic destruction, and invades the epiphysis, and can completely destroy the subchondral bone, in general, the boundary of the lesion is clear, swollen changes, within which can be seen slender bone crest, “lobulated” or “soap bubble-like” changes. “The tumor may destroy or break through the bone cortex and enter the surrounding soft tissue, forming a soft tissue mass. In some patients with unclosed epiphyseal plates, osteolytic destruction occurs in the epiphysis, which then crosses the epiphyseal plate and involves the epiphysis, and radiographs may show general features, but are not sufficient to confirm the diagnosis. Giant cell tumors of bone show osteolytic destruction with a wide migratory zone. The bone cortex of the lesion often swells and thins, and the residual bone crests within the lesion show separation on X-ray. Some aggressive osteolytic lesions have X-ray performance similar to giant cell tumors of bone, such as aneurysmal bone cysts. 2.CT examination: CT examination is more than X-ray in determining the boundary of tumor. The tumor shows solid changes, CT value is similar to muscle, sometimes the tumor contains cystic cavity, but the fluid plane is rarely seen, the reactive bone shell is different from normal bone cortex, less calcification, CT examination is helpful to clarify the relationship with articular cartilage and joint cavity and the extent of tumor invasion into surrounding soft tissues, the new double helix CT After intravenous injection of contrast agent, reconstruction at all levels can be performed to show the blood vessels within the tumor, which can replace arteriography. Magnetic resonance imaging (MRI): MRI is the best imaging method for giant cell tumor of bone, it has high quality contrast and resolution, the tumor shows low intensity signal in longitudinal relaxation time (T1-weighted image) and high intensity signal in transverse relaxation time (T2-weighted image), so it is best to use T1-weighted image to see intramedullary lesions and T2-weighted image to observe extra-cortical lesions. MRI is advantageous in showing any extracortical invasion and degree of joint involvement, while CT is characteristic for observing cortical destruction and reactive bone shell. MRI and CT are very useful for early detection of tumor recurrence, and most lesions consist of a mixture of a variable amount of surviving and necrotic tissue, such that the MRI signal is heterogeneous, with high and low signal areas existing interspersed. The spread of subchondral lesions to adjacent joints usually occurs at the point of origin and termination of intra-articular ligaments, more commonly the cruciate ligaments of the knee. When a pathologic fracture occurs, it must be examined for intra-articular spread. The appearance of the entire lesion specimen is very diverse, with some lesions consisting entirely of soft, fragile tissue with a rich blood supply and a reddish-brown color.