Using a TENS Unit for Back and Knee Pain

Before you start: the safety check

Run through these questions first. If the answer to any is yes, speak to a doctor before using TENS.

• Does your parent have a pacemaker, defibrillator or other implanted electrical device, or a serious heart rhythm problem?
• Is the pain new, severe, sudden, or worsening, or following a fall?
• Is there fever, weight loss, night pain, leg weakness, numbness in the groin or loss of bladder or bowel control? These are red flags for back pain; see lower back pain after 60.
• Is the knee hot, red, swollen or locked, which may be infection, gout or a flare; see gout in older adults?
• Is there a swollen, painful calf or a history of clots?
• Is the skin broken, rashy, thin, or numb where pads would go, as with diabetes or nerve damage?
• Does your parent have epilepsy, cancer, or confusion that would stop them reporting discomfort?
• Is the cause of the pain unknown?

If all are no, and the doctor or physiotherapist has agreed, a trial can be reasonable.

TENS for low back pain

What the evidence says. For chronic low back pain, evidence that TENS is better than placebo is weak, and some guidelines do not recommend it as a sole treatment. Some people with acute or flare-up pain feel temporary relief. Use it as a short trial, alongside gentle movement, never instead of exercise.

Pad placement. For the lower back:

• Place two pads on either side of the spine, in the painful area, about 5 to 10 cm apart, on the muscles at the sides, not directly over the bony spine. Or place pads above and below the sore spot.
• If using four pads (two channels), place them in a square or diamond around the area.
• Keep pads at least a few centimetres apart and not touching.
• Keep them away from the kidney area if you have kidney disease and have been advised to avoid it, and away from recent scars or spinal implants; ask the doctor.
• Never place pads on the front of the abdomen, chest or neck.

Positioning. Sit supported in a chair or lie on your side or front with pillows. A pillow under the knees may help when lying on the back; see lumbar cushion guide. Avoid slumped postures that pull pads off.

Settings (general). Most units have preset programmes. A common approach is a comfortable, strong but non-painful tingling, with continuous or burst mode for 20 to 30 minutes. Do not increase to the point of muscle contractions that hurt. Follow the manual and your physiotherapist's advice.

Timing. Some people use it in the morning to loosen up before activity, others in the evening to help settle. Do not use it while sleeping or driving.

Combine with:

• Gentle walking and stretching; see stretching for stiff older bodies and chair exercises for seniors.
• Heat before activity, but not at the same time as TENS on the same spot; see heat or cold for joint pain.
• Good posture and seating; see sitting for long hours and mattress firmness for back pain.
• A back belt, with care that it does not cover or dislodge pads; see back belts and lumbar supports.

TENS for knee pain

What the evidence says. For knee osteoarthritis, TENS may reduce pain for some people in the short term, but results vary and reviews find the evidence of low to moderate quality. It may be worth a trial for a person who has pain despite exercise and other measures.

Pad placement. For the knee:

• Place two pads on either side of the kneecap, on the inner and outer sides of the joint, or one above and one below the painful area. A common layout is above and below the kneecap along the line of the thigh and shin.
• Keep pads on intact, normal-feeling skin, away from scars, rashes and any swelling that is hot or red.
• Do not place pads behind the knee, where nerves and blood vessels run close to the surface, unless a physiotherapist says so.
• Keep pads off the calf if there is any chance of a clot.
• Do not put pads over the kneecap itself if it is bony and the pad does not stick well.

Positioning. Sit with the knee supported, slightly bent, and the leg resting on a stool, or lie down with a pillow under the knee. The skin should be clean, dry and free of cream; trim hair if needed.

Settings and time. As with the back: a comfortable, strong tingle without pain, 20 to 30 minutes, once or twice a day, as advised.

Combine with:

• Strengthening the thigh muscles, which is the foundation of knee care; see knee osteoarthritis at home and gentle exercises for knee and hip pain.
• A stick or support, as needed; see walking aids for knee arthritis.
• A sleeve or brace, with pads not covered by tight straps; see knee support buying guide.
• Footwear and insoles; see choosing shoes for older feet.

Judging whether it helps

Do not keep using a device that is not working. Use a simple trial:

1. Record a baseline. For a week before starting, note pain level (0 to 10) morning and evening, sleep, and what activities are limited, in a diary; see keeping a pain diary and talking to the doctor. 2. Use TENS regularly for two to four weeks as agreed, noting pain before and after sessions, and how long relief lasts. 3. Look at the pattern. Does pain fall by a worthwhile amount, such as a third? Does it allow better walking or sleep? Is the effect lasting more than the session itself? 4. Decide. If there is a clear benefit, continue and review. If not, stop, and discuss other options with the doctor. 5. Be careful about placebo effects. A new device may make people feel better for a time. A planned trial reduces the risk of spending money and time on something that does not help.

Problems and how to solve them

• The pads do not stick. Clean the skin, trim hair, replace the pads and store them properly.
• Skin redness or itching. Stop, rest for a day or two, try a different pad or placement, ask a pharmacist for hypoallergenic pads; stop if the skin blisters.
• Pain increases. Stop, review settings, and see a doctor.
• Tingling travels to unexpected places. Reposition pads.
• Muscles jump uncomfortably. Reduce intensity or change mode.
• Dizziness, palpitations, nausea or chest discomfort. Stop immediately and seek advice.
• Leg or back symptoms get worse with weakness or numbness: see a doctor urgently.

Safety reminders

• Intensity to zero before placing or removing pads.
• No use in water, shower, bath or while sleeping or driving.
• No use on the neck front, chest, head, broken skin, numb areas or over implants.
• Keep out of reach of children and confused people.
• Keep the device away from water, damp and heat.
• Replace damaged leads.
• Supervise a person with confusion.
• Do not share pads between people.

When to ask a professional

See a doctor if back pain has red-flag features, knee pain is hot, red or swollen, or if pain is worsening despite TENS. A physiotherapist can teach pad placement, settings and an exercise plan. A cardiologist must approve TENS for anyone with an implanted device. A pharmacist can advise on pads, skin irritation and medicines. See painkillers and older adults before combining with any medicines.