Case Study: Quadriceps Inhibition and TENS Post Knee Surgery

Over the past two months I’ve used TENS (transcutaneous electrical nerve stimulation) more than I ever have and with great results.

Normally, TENS is rarely used by me in treatment plans and only saved for those in severe pain needing a temporary “break”.

Lately though, TENS has been an invaluable tool in restoring quadriceps activation after knee surgery.

My friend Matt Harkey, a PhD student at UNC-Chapel Hill introduced me to this use. His research has strongly suggested that TENS is a powerful tool for improving quadriceps control after knee surgery (see references below).



Upon starting a new job, one of my first patients was a 45-year-old female four months out from ACL reconstruction. During my evaluation, I was amazed that at this point in her rehab she could still not perform a straight leg raise without a 40 degree quad lag or perform a seated knee extension beyond the same angle! I consider a proper straight leg raise a WEEK ONE task.

After two weeks of further work specifically on quad activation I sent her back to her surgeon with a request for a Nerve Conduction Velocity test. The results showed what I suspected, significant de-innervation of the quadriceps with almost no signal to the vastus medialis.

A few weeks later, I was able to meet with my PhD candidate friend who introduced me to the concept of TENS post surgery. We immediately began to implements the below protocol daily on this patient:

TENS Knee“The TENS electrodes were applied on the medial and lateral superior, as well as the medial and lateral inferior, borders of the patella. Care was taken not to place TENS electrodes on the quadriceps muscles or muscles of the anterior leg. The 2 TENS currents (pairs of electrodes) were crossed to encompass the most surface area under stimulation. Participants in each group were instructed to utilize the TENS or placebo units during all therapeutic exercise sessions and at least 8 hours per day when they were the most active.

The stimulators in the active TENS and exercise group were set to deliver a continuous TENS biphasic pulsatile cur- rent at 150 Hz, with a phase duration of 150 microseconds. Participants were instructed on how to increase and decrease amplitude, which could be adjusted between 1 and 60 mA. Amplitude was set at a strong, comfortable sensory stimulation intensity that was not strong enough to elicit muscle contraction. Participants were instructed to maintain this sensation throughout each treatment session by adjusting intensity as needed (Pietrosimone).“

Over the next few weeks, full straight leg raise was restored without quad lag. Walking, pain, light exercise all greatly improved. Most impressive, over the past five weeks, this patient gained 1.25” on her thigh circumference.

Since that time, I’ve implemented this protocol with other patients post knee-operations with continued great success. Please note, this protocol is useful for all post-op knees, not just ACL reconstructions. To learn more about this, read the following summary and see the journal articles below.



Harkey et al, 2014. Disinhibitory Interventions and Voluntary Quadriceps Activation: A Systematic Review. Journal of Athletic Training 49(3).

PIETROSIMONE et al. Effects of Transcutaneous Electrical Nerve Stimulation and Therapeutic Exercise on Quadriceps Activation in People With Tibiofemoral Osteoarthritis. JOSPT 41(1).

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  One thought on “Case Study: Quadriceps Inhibition and TENS Post Knee Surgery

  1. Yun
    October 29, 2015 at 8:16 am

    Hi, I enjoyed reading your case study. Any reasons on why you avoided placing the electrodes on the quads and anterior leg muscles? Cheers

    • October 29, 2015 at 8:19 am

      Thanks for reading. I don’t know why that was their protocol so I can’t give you specifics on why they recommend that!

  2. arkelly111
    October 29, 2015 at 11:25 am

    You can get a similar effect by applying ice to the knee before exercise!

    No need to buy or own a TENS machine. 🙂

    • October 29, 2015 at 11:26 am

      I may be wrong but I believe the studies also compared TENS and it was more effective. Would have to go back to look

      • October 29, 2015 at 11:44 am

        The systematic review was completed before some more recent research was finished…including some research that showed no difference between cryotherapy and TENS groups after 2 weeks of treatment (both improved). The point is, that a bag of ice is much readily available for most and doesn’t require the purchase of a TENS unit.

      • October 29, 2015 at 11:45 am

        Nice. Thanks for sharing that with me

  3. Jeancarlo Alencastro
    November 23, 2015 at 6:34 pm

    Which would be more useful following knee reconstruction between this TENS protocol and Russian stimulation?

    • November 23, 2015 at 6:51 pm

      According to this systematic review TENS is more effective

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