The pain in the arm and then in the leg may be due to the following reasons: 1. There may be joint inflammation involving multiple joints throughout the body, which is often seen in rheumatic and rheumatoid arthritis. The pain is wandering, i.e., this joint hurts for a while, and then it changes to other places. 2. It may be caused by mental-related factors, such as the patient is depressed recently, or suffers from autism, depression or other related diseases, and may have similar feelings. 3. For example, the patient has done excessive labor, which may cause a large amount of lactic acid deposition inside the muscles in many places throughout the body. When the patient is at rest, the symptoms of soreness may not be particularly obvious, but when the patient moves the limb, it may induce pain in a certain place because it pulls on a group of muscles. If the patient develops multiple injuries throughout the body, he or she may also experience pain here and elsewhere when doing a particular body position activity.