Design: Randomised, sham-controlled superiority trial with blinded assessment
Population: 96 adults with knee osteoarthritis on structured exercise therapy
Primary outcome: KOOS pain subscale
Effect: Adjusted difference 1.05 points (95% CI −5.19 to 7.29) post-treatment; 0.40 at 1 month

Exercise is the core of knee osteoarthritis treatment, but pain during movement can limit it. A Brazilian sham-controlled trial randomised 96 people with knee osteoarthritis on a structured exercise programme to active high-frequency TENS during exercise or sham stimulation, with blinded outcome assessment.

The KOOS pain score differed by about 1 point after treatment (95% CI −5.2 to 7.3) and 0.4 points at one month. The confidence intervals excluded the 10-point minimal clinically important difference. No secondary outcome, including strength and function, differed. No adverse effects were reported.

The trial lacked an exercise-only arm, did not formally test blinding, and followed patients for only a month. But the result is clean: TENS did not add meaningful pain relief on top of exercise.

In practice, physiotherapy time and patient money are better spent on the exercise itself than on adding electrotherapy to it.

Do not add high-frequency TENS to an exercise programme expecting extra pain relief
Keep structured, progressive exercise as the first-line treatment
Use time freed from electrotherapy for supervised strengthening and education
Weight loss and exercise remain the interventions with the strongest evidence

Why it matters

It removes a common add-on that costs clinic time without improving pain.

The statistics, in plain English

The confidence interval around the 1-point difference runs from about −5 to +7 points. Even the upper limit is below the 10-point change patients notice, so the trial effectively rules out a meaningful benefit.