Arthrogenic muscle inhibition (AMI) is a multifactorial condition which results in the inability
to fully voluntarily activate musculature surrounding an affected joint, in absence of a
structural lesion to the muscle or innervating nerve. Despite the frequent presence of AMI
following knee joint injury, the current evidence-base regarding treatments to directly
address AMI is limited. Transcutaneous electrical nerve stimulation (TENS) is a promising
disinhibitory intervention that warrants further investigation concerning its effectiveness in
counteracting the detrimental influences of quadriceps AMI.
The primary aim of this systematic review was to critically analyse and evaluate the current
evidence-base relating to the effectiveness of TENS as a disinhibitory intervention to
improve neuromuscular function of the quadriceps in pathological knee joints.
A comprehensive search of online databases including CINAHL, Medline, Embase, Scopus,
Cochrane Library, and SPORTDiscus, was conducted using pre-determined keywords to
identify relevant publications in April 2018.
All relevant studies identified using the search strategy that investigated the use of TENS as
a disinhibitory modality for quadriceps AMI and that satisfied the strict pre-determined
inclusion and exclusion criteria were accepted.
Data collection and analysis
Risk of bias and methodological quality of included studies were assessed using the 11-
point Physiotherapy Evidence Database Scale and were scored as excellent, good, fair, or
Five studies, graded as either good or poor quality, satisfied the eligibility criteria for this
systematic review. Three outcome measures were used to quantify changes in AMI following
intervention. Three included studies evaluated the disinhibitory effects of TENS within a
single treatment session with the patient at rest, while the other two included studies
observed the effects of TENS in conjunction with exercise through multiple treatment
sessions over a multi-week intervention period. All three studies examining the effects of
TENS within a single treatment session observed significant improvements in voluntary
quadriceps activation or excitability, but not for quadriceps strength. Significant
improvements were observed in voluntary quadriceps activation and strength for participants
with tibiofemoral osteoarthritis exercising with TENS. However, only large effect sizes were
found for participants with acute anterior cruciate ligament injuries exercising with TENS and
no significant improvements were observed between groups.
Based on the results from the systematic review, good quality evidence indicates TENS is
effective as a disinhibitory intervention for quadriceps AMI immediately upon application, and
when used as an adjunct therapy to therapeutic exercise for short-term benefits in voluntary
quadriceps activation and strength. Greater clinical effects may be observed in participants
with chronic knee pathologies who demonstrate persistent quadriceps weakness compared
to severe acute knee injuries. Further research is required to determine the precise neural
pathways by which the disinhibitory mechanisms of TENS operates, as well as optimal
TENS dosage to produce the greatest clinical effects.||en