A TENS unit can reduce knee pain by sending mild electrical pulses through adhesive pads placed on the skin around your knee. The key to getting results is placing the electrodes in the right spots, choosing appropriate settings, and running sessions long enough to matter. Sessions lasting 40 minutes or longer consistently produce better pain relief than shorter ones, and most people can safely use their device multiple times a day.
How TENS Reduces Knee Pain
TENS works through two complementary mechanisms. The electrical pulses activate large nerve fibers near the skin’s surface, which sends signals to your spinal cord and brain that essentially compete with pain signals and dampen them. At the same time, TENS triggers the release of your body’s natural painkillers, including endorphins and enkephalins, into your bloodstream and spinal fluid. Both high-frequency and low-frequency settings produce this opioid-like effect, though they activate slightly different receptor pathways.
Beyond blocking pain signals, TENS can restore your body’s own pain-modulation system. In people with chronic pain conditions, the brain’s ability to dial down pain signals often becomes impaired. Regular TENS use helps recalibrate that central inhibitory system, which is why consistent use over days and weeks tends to work better than a single session.
Where to Place the Electrodes
Electrode placement matters more than most people realize. A 2025 study in Pain and Therapy identified four high-density nerve areas around the knee that produce the best results when targeted with TENS pads. All four are clustered near the kneecap, and you can locate them using your kneecap width as a measuring guide.
The Four Target Areas
- Above the kneecap (quadriceps tendon): Place the bottom edge of the electrode about one-quarter of your kneecap’s width above the top of the kneecap, shifted slightly toward the inner (medial) side.
- Below the kneecap (patellar ligament): Place the top edge of the electrode about one-quarter of your kneecap’s width below the bottom of the kneecap, again shifted slightly inward.
- Inner knee joint line: Find the crease on the inner side of your knee where the thigh bone meets the shin bone. Place the electrode so its top edge sits about one-fifth of your kneecap’s width below this line, roughly one-fifth of your kneecap’s width away from the inner edge of the kneecap.
- Upper inner knee: Place this electrode about one-third of your kneecap’s width above the inner joint line, roughly one-fifth of your kneecap’s width from the inner edge of the kneecap.
If your TENS unit has two channels (four pads), a practical setup is one pad above the kneecap and one below it on the first channel, then two pads along the inner knee on the second channel. This surrounds the joint and covers the areas with the densest nerve supply. If you only have one channel (two pads), start with the above-and-below-the-kneecap placement, which brackets the joint and is the simplest to get right.
Avoid placing electrodes directly on top of the kneecap itself. The skin there sits right over bone with little soft tissue, which makes the stimulation uncomfortable and less effective.
Recommended Settings
Most consumer TENS units let you adjust three things: frequency (measured in Hz), pulse width (measured in microseconds), and intensity (how strong the stimulation feels). Here’s how to set each one.
Frequency: High-frequency TENS, typically between 80 and 120 Hz, produces a buzzing or tingling sensation and works well for general knee pain. Low-frequency TENS, around 2 to 10 Hz, produces a tapping or pulsing sensation and causes visible muscle twitches. Both reduce pain through slightly different pathways. If you’re new to TENS, start with high-frequency settings since they tend to feel more comfortable. You can alternate between high and low frequency across sessions to prevent your body from building tolerance to one mode.
Pulse width: A pulse width between 100 and 200 microseconds works for most knee pain applications. Wider pulses (closer to 200) recruit more nerve fibers and feel stronger at the same intensity level.
Intensity: Turn the intensity up until you feel a strong but comfortable tingling. You should not feel pain. For high-frequency TENS, aim for a sensation that’s clearly noticeable but doesn’t make the muscles contract. For low-frequency TENS, increase intensity until you see a gentle muscle twitch. During a session, your nerves adapt and the sensation fades, so bump the intensity up periodically to maintain that strong-but-comfortable level. Keeping the stimulation perceptible throughout the session is important for effectiveness.
Session Length and Frequency
Longer sessions produce better results. A meta-analysis of TENS for knee osteoarthritis found that sessions lasting 40 minutes or more delivered meaningfully greater pain relief than shorter ones. If you’re short on time, even 20 minutes provides some benefit, but plan for 40 to 60 minutes when possible.
You can use a TENS unit multiple times per day. Some people run two or three sessions daily, particularly during flare-ups. There’s no strict maximum, though giving your skin a break between sessions helps prevent irritation under the electrode pads. Many people find it helpful to use TENS before activities that typically aggravate their knee (walking, stair climbing, exercise) or during rest periods afterward.
Getting Better Results
Clean, dry skin improves electrode contact and makes stimulation more even. Shaving the area around your knee before applying pads also helps them stick properly. Electrodes lose their adhesive over time, and worn-out pads create patchy stimulation that feels uncomfortable and works poorly. Replace them when they stop gripping the skin firmly, which typically happens every 15 to 30 uses depending on the brand.
Position your knee comfortably before starting. You can use TENS while sitting, lying down, or even during gentle movement like walking, though pads may shift during activity. If your pain is primarily on one side of the knee, you can adjust pad placement to focus on that area while still keeping the electrodes on either side of the painful zone so the current passes through it.
Tolerance is a real issue with daily use. If you notice the same settings producing less relief over days or weeks, try switching between high-frequency and low-frequency modes, changing the pulse width, or varying electrode positions slightly. Alternating parameters from session to session helps maintain effectiveness over the long term.
Safety Considerations
TENS is considered safe for most people with knee pain, including those who have had knee replacement surgery with metal implants. The electrical current used in TENS units is too low to interfere with orthopedic hardware.
The primary group who should not use TENS is people with cardiac pacemakers, cardiac arrhythmias such as atrial fibrillation or atrial flutter, or congestive heart failure. The electrical stimulation can potentially interfere with implanted cardiac devices. If you have any heart condition, check with your cardiologist before using TENS.
Other situations to avoid TENS: don’t place electrodes over open wounds, broken skin, or areas of active infection around the knee. If you develop persistent redness or a rash under the pads, switch to hypoallergenic electrodes or try a different brand. Some skin irritation is caused by the adhesive rather than the electrical stimulation itself.