Clinical features: 1. The most common bone tumor, accounting for 12-25% of all bone tumors. 2. A tipped or broad-based mass protruding from the bone surface with a smooth cartilage cap on the surface. The central part is the marrow cavity-like structure of normal bone. 3.It can be single or multiple, and multiple cases have a genetic predisposition, which is called familial multiple osteochondromatosis. 4.Most of them are asymptomatic, mostly found by chance. If the tumor is large or located in a special area, symptoms or signs such as pain, pressure and deformity may appear. Treatment options: Most of them can be observed clinically and do not need surgery. Consider surgery when the following conditions occur 1.Significant symptoms 2.Prevention or correction of deformity 3.Malignant change or suspected malignant change 4.Improve appearance for cosmetic purposes