Electical Stimulation Explained
Electrical stimulation has been used to decrease both acute and chronic pain. How electrical stimulation works is not precisely understood, though it is thought to block the transmission of pain signals along nerves. Electrical stimulation is also thought to provoke the release of endorphins -- the body's natural painkillers.
How Is Electrical Stimulation Done?
Commonly used electrical stimulation devices apply electrical stimulation to nerves and muscles via adhesive pads placed on the skin. Some devices use alternating current, while others use direct current.
Placement of the adhesive pads matters. You should not have the pads placed over your heart or over pacemaker leads. The pads also should not be placed on your throat, over a pregnant uterus, over infection, or over malignancies.
Types of Electrical Stimulation
There are three different types of electrical stimulation. The different types produce different frequencies, waveforms, and effects.
- Transcutaneous Electrical Nerve Stimulation (TENS)
- Interferential Current (IFC)
- Galvanic Stimulation (GS)
TENS units, used to treat neuromusculoskeletal pain, are designed for at-home use. They are about the size of a cigarette pack or a deck of cards. There is a wide range of cost for a TENS unit -- between $250 and $700. You are able to adjust the intensity of the electrical stimulation. Some units allow you to choose between high and low frequency stimulation. High frequency electrical stimulation can be tolerated for hours, but pain relief is often of shorter duration than what is achieved with low frequency electrical stimulation. Low frequency is less comfortable and only tolerable for 20 to 30 minutes -- but pain relief lasts longer.
IFC is a deeper form of TENS. IFC may work by disrupting pain transmission at the spinal cord level. IFC penetrates the skin more deeply and with less discomfort. The cost is approximately $2000/unit.
GS has been used to reduce pain after nerve injuries or strains, and to enhance wound healing. With GS, a pulsed electric current is applied to body tissues to stimulate muscle contraction. GS uses a direct current, instead of the alternating current that is used by TENS and IFC. The direct current creates an electrical field over the area being treated, which can alter blood flow. The cost of GS is about $200-$300.
Electrical Stimulation for Knee Osteoarthritis
A meta-analysis of 18 small trials involving 813 patients evaluated the effectiveness of electrical stimulation for knee osteoarthritis. TENS was used in 11 of the 18 trials, while there were 4 trials of IFC, 2 trials of GS, and one that utilized both TENS and IFC.
Researchers concluded it was not possible to confirm that electrical stimulation is effective for pain relief or that it improves joint function. The meta-analysis only found small trials -- and researchers felt the quality of those was uncertain. Better-designed trials are needed if conclusions about electrical stimulation for knee osteoarthritis are to be drawn, according to researchers.
Electrotherapy. spine-health.com. Accessed 02/12/11. http://www.spine-health.com/treatment/pain-management/electrotherapy
Rutjes AWS, et al. Transcutaneous electrostimulation for osteoarthritis of the knee. Cochrane Database of Systematic Reviews 2009, Issue 4. Art. No.: CD002823. http://summaries.cochrane.org/CD002823/transcutaneous-electrostimulation-for-osteoarthritis-of-the-knee