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When you have an injury or illness, certain nerves send pain signals to your brain. With chronic pain, these pain signals keep going for weeks, months, or even years after you recover.
Chronic pain can develop after a major injury or illness, such as a back injury or shingles. Or it can happen without a known cause. It's also possible that certain brain chemicals that usually suppress pain stop working the way they're supposed to.
The cause of the pain may vary, depending on where it occurs. Pain can affect:
Muscles, bones, and joints.
This pain can happen from injuries or muscle strain. Health problems like osteoarthritis, rheumatoid arthritis, and fibromyalgia also can cause it.
Nerves and the nervous system.
This type of pain happens because of pressure on nerves or damage to them from an injury or a health problem. Sometimes pain occurs when something goes wrong with the central nervous system. This can happen with diabetes, shingles, and sciatica, for example.
Pain in your organs occurs because of injuries, infections, or health problems such as inflammatory bowel disease, irritable bowel syndrome, pelvic pain, and stomach ulcers.
You can have more than one kind of pain at the same time. For example, fibromyalgia can cause pain in muscles and nerves.
Clinical trials are research studies that evaluate a new medical approach, device, drug, or other treatment. As a Stanford Health Care patient, you may have access to the latest, advanced clinical trials.
Open trials refer to studies currently accepting participants. Closed trials are not currently enrolling, but may open in the future.