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Neuromuscular De!cits Following Anterior Cruciate
Ligament Reconstruction Require Increased Duration of 
Rehabilitation in Collegiate Athletes

by Mallory L. Heinzerling & Estephania D. Nunez 

Introduction
 One in four athletes who have experienced 
an anterior cruciate ligament (ACL) injury will 
experience a second ACL rupture within the !rst 
year of returning to their sport.1 Furthermore, one 
in three athletes experience a general re-injury to 
the knee within the !rst two years following anterior 
cruciate ligament reconstruction.2 "is illustrates 
the importance of comprehensive and e#ective 
rehabilitation and return to sport progression 
following ACL reconstruction not only for injury 
prevention, but also for long term health of the 
athletes. Anterior cruciate ligament (ACL) injuries 
are prevalent among collegiate athletes and o$en 
require surgery and extensive rehabilitation. To our 
knowledge, no systematic review exists analyzing 
the relationship between the length of recovery 
time and reinjury rates attributed to neuromuscular 
de!cits in collegiate athletes who have undergone 
anterior cruciate ligament reconstruction (ACLR). 
Despite advancements in surgical techniques 
and rehabilitation, reinjury rates remain a large 
concern with a considerable number of these 
instances attributed to neuromuscular de!cits. "is 
paper aims to address the need for comprehensive 
rehabilitation a$er ACLR that speci!cally addresses 
neuromuscular speci!c rehabilitation.

De!nitions
 In relation to this paper, the following terms 
will be used, and their de!nitions will be as 
follows. Neuromuscular de!cits are impairments to 
coordination, control, and communication between 
the nervous system and muscles. Neuromuscular 
rehabilitation consists of targeted exercises and 
interventions which assess neuromuscular de!cits 
that resulted from the initial anterior cruciate 
ligament injury. Neuromuscular reeducation is the 
retraining of the neuromuscular system to perform 
movement patterns correctly, as well as enhancing 

neuromuscular control and proprioception. "is 
term will be used synonymously with neuromuscular 
reconditioning and neuromuscular retraining. 
Neuromuscular control is the ability of the nervous 
system to coordinate muscle activity to produce 
coordinated movements of the body. 

Methods
 Studies were included that related to 
neuromuscular recovery and rehabilitation a$er 
anterior cruciate ligament repair. Only studies 
with a publication date between 2019 and 2024 
were considered. Some studies were found through 
the “cited in” tool in older articles, to maintain the 
publication time criteria. Eight articles were found 
that matched criteria for the search. "e search 
terms used were “neuromuscular,” “anterior cruciate 
ligament,” “reconstruction,” “neuromuscular 
de!cit,” “anterior cruciate ligament reconstruction,” 
“athletes,” and “collegiate athletes.” 

Results
 In total, sixteen studies were analyzed for 
synthesis in this systematic review. Two of these 
studies were systematic reviews of the literature on 
neuromuscular control and the risk of ACL reinjury 
in return to sport. Eight of these studies addressed 
recommendations for comprehensive rehabilitation 
and return to sport criteria. Six of these studies were 
experimental and analyzed with the STROBE scale 
criteria. All studies passed the STROBE scale criteria 
(see Table 1 in Appendix).

Comprehensive Rehabilitation
 "e need for comprehensive rehabilitation 
that addresses all impairments following anterior 
cruciate ligament reconstruction is a main focus of 
the current literature. Rehabilitation should begin 
as soon as possible a$er ACLR surgery, particularly 
on the non-injured leg to reduce loss of muscle 



Neuromuscular De!cits Following Anterior Cruciate Ligament Reconstruction

Aisthesis      Volume 16,  202578

strength. "irty percent or more athletes sustain an 
injury within the !rst two years of returning to sport; 
comprehensive rehabilitation is necessary to address 
this issue.3 A variety of exercises must be components 
of the rehabilitation protocol, including strength 
training, plyometrics, neuromuscular training, 
and cardiovascular conditioning. Furthermore, 
quadriceps muscle strength de!cits are a larger 
problem within ACLR patients that needs to be 
addressed in all stages of rehabilitation to adequately 
restore the strength.4-7  Even with the current 
rehabilitation protocol, strength de!cits throughout 
the leg can be seen up to !ve years following injury.8 
When quadriceps strength is not adequately restored 
during rehabilitation, athletes are at a much greater 
risk of reinjury. "is is a major issue that needs to 
be addressed and investigated to prevent long-term 
chances of reinjury in athletes. An example of the 
current protocol from Sanford Health can be seen in 
Table 29 (See Appendix). 

Return to Sport
 Following the early, mid, and late stage of 
rehabilitation, athletes will progress towards 
clearance to return to sport, which is the !nal 
stage of comprehensive anterior cruciate ligament 
rehabilitation. However, 35-40 percent of athletes that 
elect to have anterior cruciate ligament reconstruction 
do not return to sport a$er their injury, with 20-25 
percent of athletes being completely unable to due 
to residual pains and injuries.3 "e return to sport 
progression is recommended to begin with on-!eld 
rehabilitation, then progress into return-to-team 
training, and !nally return to competition.3 "ere 
are milestones within each of these progressions that 
should be met before advancing onto the next stage 
in order to lower risk of reinjury. Only one study 
was found proposing a !ve stage return to sport 
rehabilitation program that focuses on addressing 
“impairments associated with neuromuscular 
performance, movement quality, and sport speci!c 
performance” to fully prepare athletes for return to 
sport and subsequent competition. It is essential for 
athletes to meet all return to sport criteria before they 
return to competition, as they are 25 percent more 
likely to sustain a reinjury to the ACL if they fail to 
achieve this criteria.3 "is criteria should include 
assessments of single leg drop biomechanics, rate 

of force development, single limb stability, isolated 
strength techniques, torque through full range of 
motion in the knee, interlimb symmetry, and other 
various assessments that assist in the decision of 
return to sport.1,3,6-7,10-11 Additionally, this criteria 
should include restoring change of direction ability, 
bilateral de!cits in proprioception that lead to 
longer time to stabilization, the addition of cognitive 
demands into tasks, lower limb performance in 
multiple directions, capacity to cope with demands 
of the sport both physically and mentally, and 
further neuromuscular control.2-4,11-12 Meeting the 
milestones previously described is essential for 
an athlete's recovery and improving the chances 
of returning to sport without reinjury. Another 
study suggests a di#erent !ve stage return to sport 
progression including “resumption of noncontact 
practice, followed by small sided contact practices, 
full unrestricted practice, return to competition at a 
restricted workload, and last, return to competition 
unrestricted.”5 However, this protocol can be hard 
to implement without adequate support from 
healthcare professionals, such as physicians and 
athletic trainers. "e return to sport progression in 
this study is a longer progression than the previous 
study, but it progresses the athlete in smaller, more 
speci!c steps to help reduce the risk of reinjury 
upon full return to competition. While there are 
multiple suggestions for return to sport progression, 
it remains the most important part of rehabilitation, 
regardless of the di#erent progressions. "ere needs 
to be athlete supervision from a healthcare worker to 
decide on the progressions through return to sport, 
which is not addressed in the current protocol. 

Neuromuscular Reeducation
 A two-year recovery period is optimal for 
neuromuscular re-education to provide adequate 
time to address the de!cits lost following injury and 
surgical intervention. As of now, the recommended 
rehabilitation and return to sport timeline is 9-12 
months to allow for gra$ healing.5 However, this 
timeline does not allow for su%cient neuromuscular 
retraining to address the persistent neuromuscular 
control de!cits a$er ACLR. Athletes are at the greatest 
risk of reinjury within the !rst two years, mainly due 
to the persistence of these de!cits.5 "e addition of a 
neuromuscular training program into rehabilitation 



Neuromuscular De!cits Following Anterior Cruciate Ligament Reconstruction

Aisthesis      Volume 16,  202579

shows a reduction in de!cits in knee biomechanics 
which is associated with a lower risk of reinjury to 
the ACL.10 "is neuromuscular training can restore 
adequate muscle function and performance. "ere 
are multiple areas of neuromuscular de!cits that 
need to be reeducated throughout rehabilitation. 
Explosive neuromuscular power (strength and 
power training) and lower limb performance should 
be tested and addressed in late stage rehabilitation, 
a$er the athlete has met the criteria of 80-90 percent 
limb symmetry.2-3 Gait alterations stemming from 
neuromuscular dysfunction are considered to be 
a part of the neuromuscular issues resulting from 
ACLR, and need to be addressed in neuromuscular 
retraining.2,4 In order for rehabilitation to be 
comprehensive, it needs to include tasks for restoration 
of neuromuscular control and performance.2 To 
adequately reeducate the neuromuscular processes 
of the body, neuromuscular control de!cits need to 
be addressed throughout the stages of rehabilitation, 
and following return to sport. A suggestion for an 
adequate rehabilitation timeline is presented and 
compared to the current protocol in Table 39 (See 
Appendix).

Neuromuscular Rehabilitation
 Neuromuscular rehabilitation needs to be 
implemented throughout the stages of rehabilitation 
to accurately prepare an athlete for return to sport. 
Internal stimuli demands and kinesiophobia need 
to be considered on an individual basis throughout 
rehabilitation, so they cannot be generalized into 
protocol. However, ACL injuries occur most 
frequently when external stimuli are present in the 
situation that causes the athlete to fail to maintain 
neuromuscular control.3 When these cognitive 
demands and external stimuli are added, athletes have 
a much greater risk of reinjuring their ACL. "is risk 
increases substantially due to insu%cient recovery 
of neuromuscular control during rehabilitation.4,11 
Additionally, rehabilitation of sensorimotor control 
(nerve actions involving both sensory and motor 
pathways) is essential for movement control 
during on-!eld practices and play.3 Return to sport 
clearance should not occur until sensorimotor 
control is reestablished in the body. Furthermore, 
the current criteria for neuromuscular rehabilitation 
does not extend past return to sport. Neuromuscular 
testing needs to be continually addressed, even 

a$er the athlete has completed comprehensive 
rehabilitation and subsequent return to sport to 
ensure the athlete has retained the bene!cial e#ects 
of neuromuscular rehabilitation.5-6,10 "e length 
of time that neuromuscular testing needs to be 
continually addressed is unknown and is a necessary 
area for future research. Without this continuation 
of neuromuscular control testing, athletes become 
more susceptible to reinjury of the knee joint within 
the !rst few years of returning to sport and in the 
long term.

Proprioception and Biomechanics
 Proprioception allows the body to sense its 
movement and location in the environment, 
illustrating its importance in neuromuscular 
training. When athletes fail to restore the changes 
in their proprioception, knee de!cits persist a$er 
returning to sport, and the athlete becomes 30-
40% more likely to sustain a subsequent ACL 
injury.10  "ese subsequent injuries are largely due 
to the disruptions within the a#erent impulses and 
mechanoreceptor in the ACLR leg that reorganize 
the central nervous system processes involved in 
controlling and stabilizing the knee joint, and the 
proprioceptive impairments in the sagittal and 
transverse planes.1,4,6,11-13 Cutting and change of 
direction athletes work in these planes, illustrating 
the need for its consideration in neuromuscular 
rehabilitation. Neuromuscular rehabilitation needs 
to include restoration of these impairments and 
control before the athlete returns to sport. 
 Altered biomechanics a$er anterior cruciate 
ligament injury and subsequent reconstruction are a 
large focus of rehabilitation. "e retraining of bodily 
movements is an essential milestone in neuromuscular 
rehabilitation to address impairments throughout 
the kinetic chain. It is important to include practice 
for relearning various movement coordinations 
during function tasks in rehabilitation to address the 
“biomechanical and neuromuscular control de!cits” 
that persist.1-3,6,13 "ese biomechanical di#erences 
can be seen in both the injured and uninjured limb 
following ACLR.13 With this information, it becomes 
necessary to address altered biomechanics in early 
stages of rehabilitation to prevent persistent de!cits 
along the entirety of the kinetic chain that may lead 
to reinjury. 



Neuromuscular De!cits Following Anterior Cruciate Ligament Reconstruction

Aisthesis      Volume 16,  202580

Limitations
 "is study is the !rst, to our knowledge, that 
analyzes the relationship between the length 
of recovery time and reinjury rates attributed 
to neuromuscular de!cits in collegiate athletes 
who have undergone anterior cruciate ligament 
reconstruction. Additionally, many of the studies 
cited in this review are the !rst study of their topic in 
the sports medicine literature. "is review and many 
of the included studies do not take gender, gra$ type, 
or fatigue into consideration with neuromuscular 
de!cits and their persistence a$er returning to sport. 
Future research is needed to address disparities in 
the reinjury rates related to these factors, including 
the length of time that neuromuscular testing should 
continue a$er athletes return to sport. Furthermore, 
limitations exist in the research on kinesiophobia in 
athletes a$er returning to sport. Athletes not being 
mentally ready for returning to the demands of their 
sport can increase their risk of reinjury. 

Conclusion
 Understanding the implications of recovery 
duration on neuromuscular rehabilitation and 
reinjury rates is crucial for sports medicine 
professionals, coaches, and athletes. It is important 
for developing appropriate rehabilitation strategies 
and injury prevention protocols for collegiate 
athletes that have undergone ACLR that address 
neuromuscular de!cits comprehensively, not 
only for return to sport, but for lifelong function. 
"e alarming statistics in terms of reinjury rates 
among athletes highlights the need for e#ective 
strategies in restoring neuromuscular de!cits before 
returning athletes to sport. Continual assessment of 
neuromuscular function beyond return to sport is 
also essential to address persistent de!cits and their 
chances of increasing reinjury risk. Future research 
is needed to address why the current return to sport 
testing is failing to restore the variables of the criteria, 
underlying alterations in biomechanics, and further 
issues that persist a$er ACLR that place athletes at an 
increased risk of reinjury.3-4,11 

References
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4. Chou T-Y, Huang Y-L, Leung W, Brown CN, 
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8. Bagley MC, Harper SA, McDaniel J, Custer L. Single 
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00263-7



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Appendix



Neuromuscular De!cits Following Anterior Cruciate Ligament Reconstruction

Aisthesis      Volume 16,  202583


