Immediate Effects of
Therapeutic Ultrasound on Quadriceps Spinal Reflex Excitability in Patients
with Knee Pathology

GE., Saliba SA., Hart JM. Archives of Physical Medicine and Rehabilitation.
2015. Ahead of Print

Take Home Message: Quadriceps
excitability was greater 20 minutes
following non-thermal therapeutic ultrasound compared with a sham treatment
among individuals with a history of knee injury and quadriceps dysfunction.

a knee injury many patients have persistent muscle weakness, which may be
influenced by arthrogenic muscle inhibition, which is a diminished ability to activate healthy
peri-articular muscle tissue in the presence of joint pathology. This
inhibition may be due to abnormal sensory information from joint
mechanoreceptors. A therapeutic modality involving mechanical vibrations, such
as low-intensity continuous ultrasound, may reduce muscle inhibition if it is able
to stimulate receptors in peri-articular tissue via mechanical stimulation.
Therefore, the authors conducted a randomized trial among patients with a
history of knee injury and quadriceps dysfunction to compare quadriceps spinal-reflexive
excitability after a single treatment of non-thermal ultrasound or a sham
treatment. Thirty recreationally active participants with a self-reported
history of a diagnosed knee injury and quadriceps dysfunction volunteered for
this double-blinded randomized control trial. The authors measured a participant’s
baseline quadriceps spinal-reflexive excitability in both legs by measuring the
Hoffman’s reflex
using electromyography
and electrical stimulation to the femoral nerve. They also measured the peak
muscle activation that could be elicited by electrical stimulation so that they
could normalize the Hoffman’s reflex to the peak muscle response (H:M ratio).
To confirm the baseline measurements the authors repeated them on the involved
limb. After baseline testing, a blinded clinician applied ultrasound (1MHz
frequency, 0.3W/cm2 intensity, 100% duty cycle; 15 participants) or a sham
(0MHz, 0W/cm2; 15 participants) treatment to the involved anteromedial knee for
17 minutes. Lastly, the researchers measured the quadriceps spinal-reflexive excitability
immediately following treatment as well as 20 minutes post treatment in the
involved limb. Overall, participants’ knee extension strength and quadriceps
spinal-reflexive excitability were both diminished in the involved leg compared
to the uninvolved leg. The ultrasound group had 14-19% better quadriceps
spinal-reflexive excitability 20 minutes post ultrasound application compared with
the sham group. There were no differences detected during the baseline tests or
immediately after treatment.

dysfunction following an injury can lead to numerous impairments detrimental to
joint health. Modifying afferent signals to the central nervous system could
assist in altering quadriceps dysfunction. For example, non-thermal ultrasound,
which may stimulate receptors in peri-articular tissues, led to less quadriceps
dysfunction 20 minutes following treatment. This supports the contribution of
peripheral receptors to an arthrogenic response among patients with persistent
quadriceps dysfunction. This non-invasive modality demonstrated a significant
effect from a wide variety of knee injuries (anterior cruciate ligament, medial
meniscus, chondromalacia), which suggests it could work among a diverse group
of patients. It should be noted that the magnitude of change between
non-thermal ultrasound compared to sham was low. More research is necessary to
establish optimal treatment parameters, and determine clinical outcomes. In the
meantime, this research demonstrates that medical personnel could use non-thermal
ultrasound to stimulate reflex pathways, which could optimize therapeutic
rehabilitation exercise conditions 20 minutes post treatment.

Questions for Discussion:
Would you consider using nonthermal ultrasound on patients with quadriceps
dysfunction? Do you think this would have a similar effect on another joint?
What current modalities do you use for knee injuries? What do you usually use
ultrasound to treat?

by: Jane McDevitt, PhD
by: Jeff Driban


ACL Injuries are Getting on My Nerves

Norte GE, Saliba SA, & Hart JM (2015). Immediate Effects of Therapeutic Ultrasound on Quadriceps Spinal Reflex Excitability in Patients with Knee Pathology. Archives of physical medicine and rehabilitation PMID: 25839089