Starting electrical stimulation in the first week after knee surgery

After knee surgery, every day without a contraction has a cost: the role of electrical stimulation

September 2026 · Professional Resource

A contraction that does not wait for the command

In the first days after knee surgery, the quadriceps does not respond, or barely. The patient tries to contract, the muscle stays soft, the patella hardly moves. This is arthrogenic muscle inhibition, and for as long as it lasts, the muscle loses strength every day. Neuromuscular electrical stimulation was designed for exactly this window.

The principle is simple. Electrodes placed on the quadriceps deliver a current that triggers the contraction directly in the muscle. The voluntary command, held back by the operated knee, is no longer the only route. The muscle contracts fully (the patient sees it, feels it) during the days when it cannot yet do so on its own.

In concrete terms: the quadriceps works from the return home, several times a day, between physiotherapy sessions. It does not sit on standby waiting for the command to come back.

What the guidelines say

Electrical stimulation is one of the few rehabilitation tools explicitly recommended by the major guidelines:

• After ACL reconstruction, the American Physical Therapy Association guideline recommends using it for 6 to 8 weeks to increase quadriceps strength. It is the highest level of recommendation in that document.¹
• The Aspetar consensus (Doha) recommends it from the very early phase, to stimulate activation and limit atrophy, with 93% agreement among the experts.²
• After total knee replacement, the APTA guideline recommends it for strength, walking and patient-reported outcomes.³

Behind these recommendations, converging meta-analyses: after ACL surgery as after knee replacement, adding electrical stimulation to rehabilitation improves quadriceps strength, and after knee replacement the gain is still measurable one year after the operation.^4,5

Start in the first week

It is the most important result in this whole literature, and the least applied.

When the trials are compared by the moment stimulation started, the gap is clear: starting in the first week gives about three times more effect on strength than a later start.⁴ In the reference trial after knee replacement, stimulation began 48 hours after surgery.⁶

The decisive parameter is therefore the timing, not the device. The first week is when the muscle is most cut off from its command, so it is when a contraction triggered from the outside brings the most. All the reviews agree: start within the first two weeks, several sessions a day, at the maximum tolerated intensity.^8,9

A patient who goes home on day three with a stimulator set to your protocol does not wait for the first physiotherapy session for the quadriceps to work.

Raise the intensity at every session

The second decisive parameter is the strength of the contraction obtained. Gains follow intensity almost step for step: in the study that compared one leg at the maximum tolerated intensity and the other at half, the correlation between intensity and strength gain was 0.80.⁷ A comfortable stimulation maintains; a strong stimulation strengthens.

Hence the clinical instruction: aim for at least half of the maximal voluntary contraction, and increase at every session. The patient must be told from the start: at the dose that strengthens, stimulation is uncomfortable. It is not a flaw, it is the sign that the muscle is working.⁸

What helps go higher: large electrodes over the motor points, skin washed with soap and water (never alcohol, which increases resistance), the knee in extension, and the patient in control of the intensity once trained.⁸

Electrical stimulation and exercise work together

The two are not in competition, they take over from each other.

In the first weeks, when the command is cut off, electrical stimulation makes the muscle work where exercise cannot yet load it enough. It maintains volume, maintains strength, and helps voluntary recruitment come back.

As the patient recovers the command, exercise takes a growing share, and electrical stimulation keeps supporting it over 6 to 8 weeks, as a complement. This is what the reference review on inhibition describes: electrical stimulation combined with exercise helps limit the loss of strength and volume in the early phases and improves voluntary recruitment; it is most beneficial early in recovery.⁹

The patient who combines both from the start has no lost week.

In practice