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Does a TENS Unit work for Knee Pain?

If you really think about it, it’s amazing how the knee is capable for allowing the human body to perform all sorts of things. You can sit, walk, stand, run, pivot, and a whole lot more because the knee, as the human body’s largest joint, supports as throughout the day.

Because of the knee’s multiple activities, it comes as no surprise why it’s prone to injury. In fact, acute pain in the knee is one of the most common types of pain not just for the old, but young people as well (1). With this common issue, professionals have come up with several types of knee pain relief methods to help people get on with their lives, and one that’s currently gaining momentum is the TENS unit.

What is a TENS unit?

A transcutaneous electrical nerve stimulation (TENS) unit is a small, portable device operated by a battery that sends electrical signals to where the pain is, which in effect will disrupt or drown out the pain. It commonly used to help control knee osteoarthritis, but it also works as relief for muscle pain in the hips, arms, and the lower back (2). Using a TENS device may be advised by a physical therapist or any qualified professional as part of an overall treatment program.

How does it work?

In theory, a TENS machine relieves pain by delivering pulses of electrical currents through the skin. These currents enable the body to release endorphins, a hormone that blocks pain, as a result of a trigger caused by activated nerves through electrical signals.

To put it bluntly, a couple of electrodes is stuck on your skin, which then pumps and electric current through your tissues, tickling your nerves and replacing the pain with a different kind of sensation. That said, it is important to determine where exactly the pain is in order for the pads of the TENS unit to be placed correctly.

A TENS device can be fiddled to adjust the frequency and intensity of the electric current. With the right setting, it’s possible to somewhat “taze yourself” to induce electrical stimulation therapy. Kidding aside, TENS is a viable option as a drug-free treatment, that is if there isn’t a need for medication (3).

Is TENS effective?

Before we delve into that deeper, it should be known that a TENS device can be bought over the counter (OTC); this allows people who are dealing with pain experience its benefits. However, improper placing of the electrode pads may cause more harm than good, so training and advice of a healthcare professional should be sought before using one.

There have been studies conducted to prove how effective TENS is, but take note that the devices used in these studies were designed by the same healthcare professionals who applied it to subjects (4). This makes OTC versions highly questionable in terms of efficacy.

An even more challenging aspect of the application of TENS is that in studies where different kinds of TENS devices were used, it produced conflicting results, resulting to the method being labeled “controversial” and yet promising (5).

Redeeming TENS

While some doctors are still skeptic whether TENS should be a part of treatment for knee osteoarthritis or not, a number of physicians argue that TENS would play a huge role in pain treatment if applied correctly. In fact, a study in 2016 yielded positive results, with patients finding themselves with lower pain levels and at the same time gaining better muscle strength (6).

What prompted previous studies to fail, according to some healthcare professionals, was the use of substandard devices or setting the device to a low-intensity level. This had been previously proven in a 2007 report published in the BMC Musculoskeletal Disorders wherein the authors noted of positive results upon placing the intensity setting to high, as long as the patient is still comfortable (7).

Using TENS therapy is still a debatable subject, but one thing is certain: TENS can relieve pain in the knee caused by osteoarthritis and works best when used as short-term treatment.

What are the advantages of using a TENS machine?

Knee Osteoarthritis

As mentioned, TENS is effective in treating osteoarthritis of the knee. Researchers from the Ottawa General Hospital in Ontario, Canada used stronger pulses to treat pain in the knee resulting in increased relief (8). Patients who received TENS treatment also showed less knee stiffness.

Back Pain and Dental Pain

The University of Washington Orthopedics and Sports Medicine have concluded that using TENS can provide relief for nerve pain caused by sciatica and disc generation (9). It can also reduce inflammation of fibers in the muscle.

In a study published on the American Dental Association Journal, it was concluded that when a TENS unit is used to inhibit pain during a dental procedure, patients often come back for a follow-up checkup (10). The observation is deemed beneficial as the tendency of most patients who go through painful dental procedures often never return for a follow-up treatment.

Massage Benefits

While intended to reduce pain in a localized part of the body, some clinics that offer TENS treatment offer massages by using a TENS unit. These units are able to produce alternate levels of intensity that can benefit the body internally. OTC TENS devices can be used as massagers for those who desire relaxation at home.

When you’re decided on having a TENS device at home, consider the advice of your physical therapist or doctor. Note that he may not allow you to do so, but if it’s a yes, ask the recommended setting for intensity and frequency.

Note that TENS units commonly have either four or two electrode pads. In time, they will lose their adhesiveness, and so replacements are needed. Some pads already come with a gel, and others will require users to apply gels to the pads before use. Your budget also plays a huge role in buying this device. Typically, the ones for home use need not be expensive.


There are no known side effects to TENS, but it may not be the solution for everyone. Those who have metal implants are advised not to use a TENS machine, as well as those who have pacemakers. Your doctor can tell you where and where not to place the pads. Certain areas of the body, when touched by electro-current, could have muscle spasms. You also shouldn’t put them on irritated skin or over your eyes.

Additionally, only adults should use TENS. It it not be used by children, as well as pregnant women.

TENS may be used regularly but note that you might grow tolerant of the same frequency, rendering the device ineffective. If this happens, always check with your doctor.

It’s also quite unclear if there are reimbursements for TENS units. There might, but it could be limited. It is best if TENS treatment is prescribed by a qualified physician so you can check with Medicare if your diagnosis is covered.

Overall, you should set your expectations to a minimum. TENS is effective as short-term care for pain, so if your condition is severe, you should go for pain treatments that have been already established and are guaranteed effective. TENS is intended to assist, and not to totally replace overall treatment.


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