Transcutaneous electrical nerve stimulation (TENS) is a drug-free method of pain relief that has been used to treat a wide variety of muscle and joint problems, as well as many other painful conditions. TENS uses electrical impulses to stimulate the nerve endings at or near the site of pain, diminishing the pain and replacing it with a tingling or massagelike sensation.

TENS can be used in a health-care setting, but most often the patient uses it at home.

Researchers still are not certain exactly how TENS works. The two explanations suggested most often are that electrical stimulation of the nerves blocks the pain sensation and that TENS triggers the release of the body's natural painkillers, called endorphins.

A TENS device consists of an adjustable power unit and electrodes that attach to the power unit via wires.

Before beginning treatment, the patient must put the electrodes in place — usually on top of or next to the painful area. Patients can experiment with different locations for the electrodes to see what provides the best pain relief. In some cases, it may be more effective to position the electrodes on top of a related nerve or a site that is considered to be a trigger point or acupuncture point for the painful area.

Electrical stimulation can be used in the following ways:

TENS has been used in patients with muscular pain, osteoarthritis, rheumatoid arthritis, sciatica, pain after surgery and other conditions.

Studies have shown varying results as to how well TENS works, what types of pain it can best relieve and how long the relief lasts. Many people have found TENS helpful, however, and many doctors recommend it as part of an overall pain-management program.