About TENS / EMS Units for ACL Issues

May 23, 2025

About TENS / EMS Units for ACL Issues

Using a TENS/EMS Unit for Quad Activation After ACL Surgery

Regaining quadriceps strength after ACL (anterior cruciate ligament) surgery is one of the most important parts of rehabilitation. One helpful tool that may assist in this process is a neuromuscular electrical stimulation (NMES) unit ,often sold as TENS/EMS devices. But while they can aid quad activation, they must be used carefully and appropriately.

Patients could have very different quad activation experiences post ACL surgery. Those with something like an allograft may have little to no issues at all here as there was no harvest site for their graft.

What Is a TENS/EMS Unit?

TENS (Transcutaneous Electrical Nerve Stimulation) is primarily used for pain relief by stimulating sensory nerves.
EMS or NMES (Electrical Muscle Stimulation) targets motor nerves, causing the muscle to contract — making it useful for muscle re-education, especially in post-op patients who have difficulty firing their quad.

For ACL rehab, we’re primarily interested in the EMS/NMES function, not the TENS mode. These units may exist in your physical therapy office, but typically these will be more powerful units with more functionality that typical consumer available units.

Why Quad Activation Matters

After ACL surgery, it’s common for the quadriceps muscle (especially the vastus medialis oblique, or VMO) to shut down or atrophy due to pain, swelling, and disuse. This is called arthrogenic muscle inhibition.

Using EMS can help:

Restore the brain-to-muscle connection.
Prevent atrophy during the early phases.
Assist with proper gait and knee extension.
Lay the foundation for later strength-building.

When to Use EMS for Quad Activation

Timing: Usually safe to begin EMS for quad activation as early as Day 3 to Week 1 post-op, if cleared by your surgeon or physio.
Target: Focus on the vastus medialis (VMO) and general quad belly.
Position: Start in a seated or lying position, with the knee supported or slightly bent.
Frequency: 1–2 sessions per day, 10–15 minutes, using protocols like 10 seconds “on” and 50 seconds “off.” if cleared by your surgeon or physio.
Effort: Try to voluntarily contract your quad during the EMS pulse to reinforce neuromuscular control.

Important Warnings and Misconceptions

Don’t use EMS in place of physical therapy. It’s a supplement, not a replacement.
Do not use TENS mode for knee pain in the first few weeks or at all unless instructed by your doctor. Masking pain can lead to overuse, falls, or re-injury.
Do not place electrodes over the knee joint itself. Stick to the quad muscle belly.
Avoid if you have any implanted electronic device, metal hardware that hasn’t been cleared, open wounds, or active infection.
Always consult with your physiotherapist or surgeon before starting TENS/EMS use.

Electrode Placement Tips

Clean the skin before applying.
Place one pad on the upper quad (near the hip) and one on the lower quad (just above the knee), aligned with the muscle fibers.
Make sure the muscle contracts visibly but comfortably. More isn’t better. Don’t crank up intensity to painful levels.

Conclusion

EMS can be a powerful tool in your ACL rehab toolkit, particularly for jumpstarting quad activation when voluntary control is limited. Used properly and under guidance, it can accelerate your return to functional movement. But remember: timing, technique, and supervision matter.

Always talk to your physiotherapist before beginning EMS use. And stay focused on the full picture of your recovery.