Sports Medicine Research: In the Lab & In the Field: TENS to Treat Knee Pain Induced Quadriceps Inhibition?! (Sports Med Res)
Monday, November 23, 2015

TENS to Treat Knee Pain Induced Quadriceps Inhibition?!

Effects of transcutaneous electrical nerve stimulation on quadriceps function in individuals with experimental knee pain

Son SJ, Kim H, Seeley MK, Feland JB, Hopkins JT. Scand J Med Sci Sports. 2015: 1-11. Accessed October 4, 2015 doi: 10.1111/sms.12539
Take Home Message: Sensory transcutaneous electrical nerve stimulation may help reduce knee pain and increase quadriceps function among people with knee pain.

Knee pain inhibits muscule function. Unfortunately, we don’t know if a disinhibitory modality such as sensory transcutaneous electrical nerve stimulation (TENS) can increase motor function of inhibited muscles. The purpose of this research study was to see if sensory TENS had an influence on quadriceps muscle activation before and after the treatment. A total of 30 healthy volunteers (~24 years old) with no recent lower extremity injuries were placed into 2 groups (TENS, placebo). The placebo group was matched to the TENS group based on gender, age, mass, and height. This is important since this study is not a randomized trial. Everyone attended three sessions where they randomly received hypertonic saline infusion (pain inducing infusion), isotonic saline infusion, or no infusion (control). Participants had 2 days between sessions. At each session the researchers assessed quadriceps maximum voluntary contraction (MVC) and central activation ratio at 4 times: 1) baseline, 2) infusion, 3) treatment, and 4) post-treatment. Knee pain was recorded every 2 minutes throughout the infusion and treatment using a 100-mm visual analog scale (VAS). Two different sensory TENS channels were used to cross the knee joint. The TENS protocol was a continuous, asymmetric biphasic square-pulse wave with a pulse width of 120ms and a pulse rate of 180Hz. The intensity was set by increasing the machine until there was a visible contraction of the vastus medialis and then the intensity was decreased until the contraction was no longer seen or felt. Contact points were set 5-7cm apart surrounding the knee joint with intersecting currents. Both groups (TENS and placebo) had similar changes in MVC and CAR from baseline to hypertonic infusion recording times, but the TENS group had better quadriceps performance during the treatment and post-treatment recordings as seen by their increased MVC and central activation ratio. As for knee pain, scores peaked at 40mm during hypertonic saline infusion and remained steady in the placebo group, whereas the TENS group showed a gradual decrease on the VAS to 12mm.
Overall, sensory TENS decreased pain and increased the activation of the quadriceps muscles when compared to the placebo group. TENS is used to as a disinhibitory modality, meaning that muscle function can be improved while the muscle being inhibited. The importance and significance of these findings is that sensory TENS can be used as an immediate modality to help reduce pain and restore normal motor function in healthy individuals with knee pain. It is important to consider that TENS can be used to reduce the pain as well as helping to improve quadriceps function. However, we need to keep in mind that this was induced knee pain and so it is unclear if sensory TENS will be as effective among patients with knee pain due to injury or among patients with pain at different joints. Regardless, there is evidence to support the use of sensory TENS to reduce pain and promote muscle activation when the quadriceps are inhibited due to pain. This could potentially lead to quicker and more effective rehabilitation and help preserve joint health. Clinically, these findings should encourage clinicians that TENS may help decrease knee joint pain and facilitate better quadriceps activation among knees with pain-induced quadriceps inhibition.

Questions for Discussion:  Do you think that motor or noxious TENS prove to be more effective than sensory TENS in relieving pain and increasing muscle activation? Would there be a difference in results of the effects of TENS in acute or chronic injuries?

Written by: Damian Pulos, Ashley Schuster
Reviewed by: Jeffrey Driban

Related Posts:

Son, S., Kim, H., Seeley, M., Feland, J., & Hopkins, J. (2015). Effects of transcutaneous electrical nerve stimulation on quadriceps function in individuals with experimental knee pain Scandinavian Journal of Medicine & Science in Sports DOI: 10.1111/sms.12539


Andrea Baellow said...

I am always hesitant when "knee pain" is used so generally. There is not necessarily muscle inhibition with all knee pain. Anyways, I definitely think there would be a difference in the results in chronic vs. acute knee pain. With acute pain may come swelling, which may alter the depth of penetration of the TENS. Although the waves would be going to the same depth, if there is swelling in the area it will not be going as deep into the muscle. I would've liked to see data collected at an hour and 2 hours post treatment. If this was to be used before a game, 30 minutes may only get the athlete halfway through the warm-up. I also wonder what would happen if there was a TENS group and a TENS while exercising group (such as isometric knee extensions) to see if this helps recruit motor units.
Andrea Baellow

Jeffrey Driban said...

Thanks Andrea for the comment! I agree that we need to be wise with our choice when to use TENS. This model most likely represents a painful knee with effusion. The idea of TENS+exercise is interesting. If an athlete had notable muscle inhibition and knee effusion we should probably hold them out of the game so getting a short-term benefit from TENS may be OK. We've seen in prior posts that the presence of knee effusion is one of the main reasons an athlete doesn't return to the same level of play after an ACL injury. Furthermore, the potential for reinjury or causing long-term damage to the joint may be elevated for an athlete with effusion and muscle inhibition if returned to play. Thanks again for the comment!

Candace Bernitt said...

My understanding is that the results of this article show that TENS improved knee function in the hypertonic saline solution trial, which is the pain-inducing infusion. I am curious as to its effects on the isotonic saline solution. I believe that a swollen knee that may or may not have associated pain will still contribute to muscle inhibition. Does TENS play the same role in subjects with minimal to no pain, but who still have some sort of underlying or residual pathology?

Jeffrey Driban said...

Hi Candace:
In this study, isotonic saline had no significant effect on quadriceps muscle central activation ratio (CAR, 0% change) nor quadriceps muscle max voluntary contraction (4.5-8% change). In comparison the hypertonic solution was associated with a -10 to -11% change in CAR and a 26 to 29% reduction in max voluntary contraction. TENS didn't effect this group very much.

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