Causes of an enlarged clavicle on one side include osteophytes, soft tissue hyperplasia and edema, and clavicle fracture. The specific situation should be determined according to the doctor’s examination. 1. Osteomalacia: Unilateral clavicle enlargement may be caused by abnormal bone healing after trauma or may be caused by a traumatized surface with long-term bone grinding. When an osteophyte is present it may cause protrusion of the clavicle on one side, and may also be associated with localized pain and swelling. 2. Soft tissue hyperplasia and edema: generally refers to the local appearance of cell proliferation or edema. It is usually caused by cell proliferation, edema or heterogeneous hyperplasia due to inflammatory stimulation, traumatic stimulation or tumor invasion, and then one side of the clavicle will be enlarged. 3. Clavicle fracture: clavicle fracture is easy to occur when subjected to violence. After clavicle fracture, due to the growth of a large number of bone scabs, the fracture end can realize bony healing, and then there will be one side of the clavicle enlargement. It is recommended that when one side of the clavicle is enlarged, you should go to the hospital for a comprehensive examination in a timely manner, and carry out standardized treatment after the physician confirms the diagnosis. In order to avoid untimely treatment, leading to the aggravation of the condition and other discomforts.