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