There are several common causes of shoulder nodules: 1. There may be muscle spasm around the shoulder joint, which can be caused by a number of reasons, such as excessive activity of the upper limb or cold, or old injury, which may cause muscle spasm and produce striae or nodules. 2. For example, if the patient’s shoulder joint or back is cold or traumatically inflamed, inflammatory exudation may occur, followed by nodules and scarring. 3. The nodules are clearly palpable, and are not easily pushed and have pressure pain.