In most cases of pain, what you see-or more accurately, what you feel-is what you get. If you bump your head, your head hurts. If you have an achy left knee, the pain might be caused by osteoarthritis in that knee. A tight feeling in the middle of your chest might indicate a heart problem-or maybe not. But there are many cases in which pain in one part of the body is caused by a problem that is in a completely different location. This condition is called "referred pain," and theres a good chance, at some point, that youve experienced the problem. "I see many patients who complain of pain in their arms or legs that may be attributed to irritation of nerves in the neck or lower back caused by bulging discs or arthritis," says Bruce Vrooman, MD, of Cleveland Clinics Pain Management Department. "Others will have abdominal or back pain that may be caused by irritation of nerves in abdominal organs."