Neuromusculoskeletal alterations after ACL reconstruction: a cross-sectional study of cortical activity, motor response, and psychological readiness

Abstract

Background

Anterior cruciate ligament (ACL) injuries affect not only the musculoskeletal system but may also influence neurocognitive and psychological functions. Emerging perspectives emphasize a neuromusculoskeletal approach to post-injury recovery. However, comprehensive evaluations of brain activity, motor response, and psychological readiness—especially in comparison between primary and revision ACL cases—remain limited.

Methods

In this cross-sectional observational study, 60 male athletes aged 18–30 were allocated into three groups (n = 20 each): healthy controls, primary ACL reconstruction, and revision ACL reconstruction. Frontal cortical activity was assessed using theta/beta ratio via EEG (Nexus-10 system) during rest and cognitive task conditions. Reaction time was measured using a computer-based visual response test. Psychological status was evaluated using the Tampa Scale of Kinesiophobia (TSK-11) and the ACL–Return to Sport after Injury (ACL-RSI) scale.

Results

The mean frontal theta/beta ratio was highest in the revision group (eyes-open: 2.19 ± 0.45) compared to the primary ACL (1.92 ± 0.39) and control groups (1.61 ± 0.28; p < 0.001). Mean visual reaction times were prolonged in the revision group (293 ± 25 ms) relative to the primary ACL (278 ± 19 ms) and control groups (262 ± 18 ms; p = 0.001). Psychological evaluation revealed higher TSK-11 scores (21.1 ± 3.2 vs. 17.5 ± 2.9 vs. 13.2 ± 2.3) and lower ACL-RSI scores (65.2 ± 9.3 vs. 76.8 ± 8.5 vs. 91.4 ± 5.6) in the revision, primary, and control groups, respectively (all p < 0.001). Correlation analyses indicated strong associations between EEG indices, reaction time, and psychological scales.

Conclusion

ACL reconstruction, particularly revision procedures, may involve alterations in cortical activity, motor response, and psychological readiness. These results highlight the relevance of a neuromusculoskeletal perspective in post-ACL rehabilitation.

Trial registration

ClinicalTrials.gov NCT07163468. Registered on 01 September 2025 (retrospectively).

Introduction

Anterior cruciate ligament (ACL) injuries are among the most common and functionally disabling knee traumas, particularly in athletes engaged in high-demand sports. ACL reconstruction (ACLR) is considered the gold-standard treatment to restore knee stability and enable return to sport (RTS) [1–3]. However, despite advances in surgical techniques and rehabilitation protocols, a substantial number of athletes struggle to return to their pre-injury performance levels. This discrepancy suggests that successful RTS involves not only biomechanical restoration but also cognitive and psychological recovery processes that are often underrepresented in current rehabilitation paradigms [4–6].

Cognitive functions such as attention, inhibitory control, and decision-making have recently been linked to both injury risk and rehabilitation outcomes in athletes. Impaired executive functions may reduce the ability to process visual and proprioceptive cues under pressure, thereby increasing susceptibility to non-contact injuries and delaying neuromotor reintegration after surgery [7–11]. Several studies have indicated that athletes with ACL injuries demonstrate slower information processing, reduced cognitive flexibility, and altered cortical resource allocation during movement tasks [6, 12–14].

In recent years, there has been a paradigm shift in the conceptual understanding of musculoskeletal injuries. Increasing evidence supports the transition from a traditional “musculoskeletal” model toward a more comprehensive “neuromusculoskeletal” framework [15]. This framework emphasizes the bidirectional relationship between peripheral joint integrity and central nervous system (CNS) processing, highlighting that musculoskeletal trauma can induce cortical reorganization, altered sensorimotor mapping, and changes in attentional control mechanisms [12, 16, 17]. Studies using functional imaging and electrophysiological techniques have demonstrated changes in motor planning, prefrontal activation, and postural control patterns following ACL injuries [6, 12, 13].

Electroencephalography (EEG) provides a non-invasive and sensitive method to assess cortical dynamics in real time. Specifically, the frontal theta/beta ratio—reflecting the balance between top-down executive control (beta activity) and bottom-up cognitive engagement (theta activity)—has been widely used as an index of attentional regulation and cognitive readiness [18–20]. Elevated theta/beta ratios are considered markers of reduced attentional focus or increased mental fatigue, both of which may negatively affect motor performance. Recent research has shown that individuals with ACL injuries exhibit increased frontal theta/beta ratios during rest and cognitive task conditions, suggesting potential disruptions in cortical efficiency and attentional resource allocation [11, 21, 22].

In parallel, psychological readiness has been increasingly recognized as an important determinant of RTS after ACLR. Even when physical recovery is satisfactory, factors such as fear of reinjury (kinesiophobia), decreased confidence, and emotional maladjustment can meaningfully hinder return-to-sport participation. The Tampa Scale of Kinesiophobia (TSK-11) and the Anterior Cruciate Ligament–Return to Sport after Injury (ACL-RSI) scales are validated and reliable instruments for evaluating these domains [23, 24]. While these scales are primarily associated with psychological readiness rather than actual return outcomes, their inclusion provides insight into the emotional and cognitive components that shape rehabilitation adherence.

Despite growing awareness of the neuromotor and psychological sequelae of ACL injuries, the literature still lacks integrative, multidomain studies assessing neurophysiological, cognitive, and psychological aspects simultaneously. Moreover, while several investigations have compared primary and revision ACLR, few have included a healthy control group or addressed the clinical heterogeneity within revision cases (e.g., multiple surgeries, differing graft types, and rehabilitation exposure) [14, 25, 26]. Revision ACLR is typically associated with longer recovery, increased mechanical stress, and greater emotional burden, all of which may contribute to distinct neurocognitive profiles compared to first-time reconstructions [27].

Therefore, the present study aims to assess frontal EEG theta/beta ratios (as indicators of attentional control), visual reaction times (as a measure of neuromotor response efficiency), and psychological outcomes (TSK-11 and ACL-RSI) in athletes with a history of ACL reconstruction. These parameters were compared across three groups: healthy athletes, athletes after primary ACL reconstruction, and those after revision ACL reconstruction. By integrating electrophysiological, cognitive, and psychological data, this study seeks to provide a more comprehensive and objective understanding of post-ACL recovery dynamics.

To the best of our knowledge, this is the first study to concurrently evaluate frontal cortical activity, cognitive reaction time, and psychological readiness in healthy athletes, primary ACLR, and revision ACLR groups. The results may contribute to refining RTS decision-making and support the incorporation of neurocognitive and psychological components into evidence-based sports rehabilitation programs.

Materials and methods

Study design and ethical approval

This cross-sectional observational study was conducted under the coordination of the Department of Orthopaedics and Traumatology, Faculty of Medicine, Düzce University, in collaboration with the Departments of Sports Sciences, Physiotherapy and Rehabilitation, and Psychological Counseling and Guidance. The research protocol was approved by the Düzce University Non-Interventional Clinical Research Ethics Committee (Approval No: 2025/177, Date: 16/06/2025) and conducted in accordance with the principles of the Declaration of Helsinki (2013 revision). Each participant provided written informed consent after receiving detailed information about the study objectives, procedures, and potential risks.

All experimental sessions were conducted between 09:00 and 12:00 a.m. to minimize diurnal variability. Participants were instructed to avoid caffeine, nicotine, alcohol, and vigorous physical activity for at least 12 h before testing and to maintain their usual sleep routine. Compliance was verified verbally before data collection. These precautions were implemented to reduce the influence of arousal, fatigue, or metabolic factors on EEG recordings.

The study was carried out between June and July 2025 in a controlled laboratory environment. Data collection was scheduled to ensure that each participant completed all assessments on the same day under standardized conditions. All procedures were conducted by the same research team across disciplines to ensure methodological consistency and reduce potential bias.

Participants and sample size

A total of 60 male athletes aged between 18 and 30 years were enrolled and equally divided into three groups:

Control group

Healthy athletes with no history of knee injury or surgery.

Primary ACL group

Athletes who had undergone a single ACL reconstruction and completed rehabilitation at least six months before testing.

Revision ACL group

Athletes who had undergone at least two ACL surgeries, including one revision, and completed rehabilitation at least six months before participation.

All participants were actively engaged in regular athletic training and voluntarily agreed to participate.

For the revision group, information about graft type (hamstring tendon, bone–patellar tendon–bone, or quadriceps autograft), number of reconstructions, and time since last surgery was collected to describe surgical variability. These data were reported descriptively in the Results section but were not included as covariates in the primary analysis due to subgroup limitations.

Only male athletes were included to minimize hormonal and menstrual-cycle–related variability that could influence cortical activity and EEG parameters. This approach ensured within-group homogeneity, while its limitation regarding generalizability to female athletes was discussed later.

Inclusion and exclusion criteria

Inclusion criteria were as follows: male sex, age between 18 and 30 years, regular participation in amateur or professional sports, completion of ACL rehabilitation (for surgical groups) at least 6 months before enrollment, ability to undergo EEG and reaction time testing, and provision of signed informed consent.

Exclusion criteria included: history of neurological or psychiatric conditions (e.g., epilepsy, ADHD, depression), additional lower extremity injuries or orthopedic surgeries, metal implants or scalp conditions incompatible with EEG, uncorrected visual or auditory deficits, systemic illnesses (e.g., diabetes, multiple sclerosis, neuropathy), use of psychoactive medication, and any cognitive or physical limitation that could interfere with the testing procedures. Female participants were excluded to avoid hormonal confounding effects on EEG recordings.

Data collection procedures

All assessments were conducted in a single day in a quiet, temperature-controlled laboratory setting. First, demographic and physical characteristics such as age, height, weight, BMI, years of sports participation, dominant limb, and injured side were recorded. Subsequently, psychological questionnaires were completed, followed by EEG recording and reaction time testing. All procedures followed a standardized sequence across all participants.

Participants were seated comfortably in an adjustable chair and instructed to relax before each recording. A 5-minute adaptation period was provided to ensure stable baseline cortical activity. Data collection was postponed if participants reported fatigue, headache, or lack of focus.

Measurement tools

Psychological measures

Two validated instruments were used to assess psychological factors related to return to sport after ACL injury.

The Tampa Scale of Kinesiophobia–11 (TSK-11) is a shortened version of the original TSK and is widely used in sports medicine to evaluate fear of reinjury and movement-related anxiety [28]. It consists of 11 items scored on a 4-point Likert scale (1 = strongly disagree, 4 = strongly agree), with total scores ranging from 11 to 44. Higher scores indicate greater levels of kinesiophobia. The TSK-11 has demonstrated strong internal consistency and predictive validity in orthopedic populations, including athletes returning from ACL reconstruction.

The Anterior Cruciate Ligament–Return to Sport after Injury (ACL-RSI) scale was used to measure psychological readiness for return to sport [29]. The scale consists of 12 items assessing three dimensions: emotions, confidence in performance, and risk appraisal. Each item is scored on a visual analog scale from 0 to 100, with higher scores reflecting greater psychological readiness. The total score is calculated as the mean of all items. The ACL-RSI has been shown to be reliable and sensitive to changes over time, and is considered one of the most relevant tools for evaluating mental recovery after ACL surgery.

Neurophysiological assessment (EEG)

Frontal cortical activity was assessed using the Nexus-10 biofeedback EEG system (Mind Media, The Netherlands), a high-resolution device commonly used in clinical neurophysiological research. EEG electrodes were placed at F3 and F4 positions, targeting the dorsolateral prefrontal cortex, in accordance with the international 10–20 electrode placement system. A reference electrode was placed at the mastoid, and impedance was maintained below 10 kΩ [18, 30].

EEG recordings were obtained under three standardized conditions:

Eyes-open resting state (3 min)

Participants were instructed to fixate on a crosshair on a blank screen while minimizing movement and blinking.

Eyes-closed resting state (3 min)

Participants were instructed to relax with eyes gently closed while remaining awake.

Cognitive task condition (3 min)

Participants performed a low-load mental arithmetic task (e.g., serial 7 subtraction or backward counting), known to engage attentional and executive cortical regions.

All EEG data were band-pass filtered (1–40 Hz) and segmented by condition. Artifact removal (e.g., blink, muscle activity) was performed manually and via automated algorithms. Power spectral density analysis was conducted using Fast Fourier Transform (FFT). Mean amplitudes in the theta (4–8 Hz) and beta (13–21 Hz) bands were extracted for each condition. The frontal theta/beta ratio was computed by dividing mean theta power by mean beta power and served as an objective marker of attentional control and cognitive readiness. Although higher ratios are typically interpreted as lower attentional engagement, they may also reflect non-specific arousal or fatigue effects, which were controlled to the extent possible.

Cognitive performance measure (Visual reaction time)

Visual reaction time was assessed using a computer-based response time task developed with standardized timing protocols. Participants were seated at a fixed distance (approximately 60 cm) from a high-refresh-rate monitor. A series of visual stimuli (colored shapes) appeared at randomized intervals on the screen. Participants were instructed to press a designated response key on the keyboard as quickly as possible upon detecting the visual stimulus.

Three practice trials were provided before the actual testing session. The main test included five experimental trials, and the mean reaction time (in milliseconds) across these trials was used for analysis. The testing environment was quiet, well-lit, and controlled for temperature and external distractions. Although this simple reaction time paradigm provides precise measurement of basic neuromotor latency, it does not replicate the complex, sport-specific decision-making context. This limitation was acknowledged when interpreting the findings.

This paradigm has previously been validated in neurocognitive and sports performance research and is considered a reliable measure of sensorimotor response speed [31].

Data privacy and confidentiality

All collected data were anonymized and stored on encrypted digital devices accessible only to the research team. Personal identifiers were removed to ensure privacy, and data were used exclusively for scientific purposes in accordance with ethical guidelines.

Statistical analysis

All statistical analyses were performed using IBM SPSS Statistics version 26.0 (IBM Corp., Armonk, NY, USA). The normality of continuous variables was assessed using the Shapiro-Wilk test. For variables with normal distribution, comparisons among the three groups were performed using one-way analysis of variance (ANOVA), followed by Tukey’s HSD post-hoc test when significant differences were found. For non-normally distributed variables, the Kruskal-Wallis test was applied, followed by Dunn-Bonferroni correction for pairwise comparisons.

Categorical variables were compared using the chi-square test or Fisher’s exact test where appropriate. Correlations between EEG theta/beta ratios, reaction times, and psychological scale scores (TSK-11 and ACL-RSI) were analyzed using Pearson or Spearman correlation coefficients depending on data distribution.

All statistical tests were two-tailed, and a p-value of less than 0.05 was considered statistically significant.

Prior to data collection, an a priori power analysis was conducted using G*Power version 3.1.9.7 to determine the required sample size. Based on a one-way ANOVA model comparing three independent groups, a medium effect size (f = 0.40), alpha level of 0.05, and statistical power of 0.80 were assumed. The analysis indicated that a minimum total sample size of 48 participants (16 per group) would be sufficient [24]. To increase statistical power and account for potential data loss, the study was conducted with 60 participants, with 20 subjects per group.

Results

According to Table 1, age, weight, BMI, and years of athletic experience differed significantly among the groups (p < 0.05). The revision ACL group was notably older (28.2 ± 3.1 years), heavier (76.0 ± 6.1 kg), and had longer athletic history (9.3 ± 2.5 years) compared to the other groups. No statistically significant differences were found in height, dominant limb distribution, or side of injury. Additional surgical details of the revision group are presented in Table 2 to describe sample heterogeneity.

Table 1.

Demographic and baseline characteristics

Variables	Control (n = 20)	Primary ACL (n = 20)	Revision ACL (n = 20)	p-value
Age (years), mean ± SD	22.1 ± 1.4	25.6 ± 2.1	28.2 ± 3.1	< 0.001
Sex (M/F), n (%)	20/0	20/0	20/0	–
Height (cm), mean ± SD	178.3 ± 4.9	179.1 ± 5.2	178.6 ± 4.8	0.742
Weight (kg), mean ± SD	72.4 ± 5.2	75.1 ± 6.9	76.0 ± 6.1	0.051
BMI (kg/m²), mean ± SD	22.8 ± 1.2	23.4 ± 1.3	23.8 ± 1.4	0.066
Years of athletic participation	5.1 ± 1.6	6.7 ± 1.7	9.3 ± 2.5	< 0.001
Dominant limb (Right/Left), n (%)	19/1	20/0	18/2	0.367
Injured limb (Right/Left), n (%)	–	12/8	13/7	0.758

BMI Body mass index, SD Standard deviation

Table 2.

Surgical characteristics of the revision ACL group (n = 20)

Variable	Value
Time since last surgery (months), mean ± SD	9.0 ± 2.4 (7–14)
Number of reconstructions, n (%)	1 revision = 15 (75%); ≥ 2 revisions = 5 (25%)
Graft type, n (%)	Hamstring = 12 (60%); BPTB = 5 (25%); Quadriceps = 3 (15%)
Rehabilitation duration (months), mean ± SD	6.8 ± 1.2

Based on Table 3, frontal theta/beta ratios differed significantly across groups under all three EEG conditions. The revision ACL group consistently exhibited higher mean theta/beta ratios than both the primary ACL and control groups (p < 0.001 in all conditions).

Table 3.

Comparison of frontal EEG Theta/Beta ratios across conditions

EEG Condition	Control (n = 20)	Primary ACL (n = 20)	Revision ACL (n = 20)	p-value
Eyes open rest	1.61 ± 0.28	1.92 ± 0.39	2.19 ± 0.45	< 0.001
Eyes closed rest	1.42 ± 0.24	1.75 ± 0.33	2.06 ± 0.41	< 0.001
Cognitive task	1.18 ± 0.22	1.51 ± 0.30	1.83 ± 0.33	< 0.001

EEG Electroencephalography, SD Standard deviation

The largest between-group difference (η² = 0.36) was observed during the cognitive task condition, indicating a substantial effect size.

According to Table 4, the mean visual reaction time increased progressively from controls to revision cases. The revision ACL group displayed a longer average latency (293.2 ± 24.6 ms) compared with the primary ACL (277.9 ± 19.2 ms) and control (261.5 ± 18.4 ms) groups (p = 0.001, η² = 0.29).

Table 4.

Visual reaction time across groups

Reaction Time (ms)	Control (n = 20)	Primary ACL (n = 20)	Revision ACL (n = 20)	p-value
Mean ± SD	261.5 ± 18.4	277.9 ± 19.2	293.2 ± 24.6	0.001

RT Reaction time, SD Standard deviation

According to Table 5, psychological outcomes differed significantly among groups.

Table 5.

Psychological assessment scores

Measure	Control (n = 20)	Primary ACL (n = 20)	Revision ACL (n = 20)	p-value
TSK-11 Score	13.2 ± 2.3	17.5 ± 2.9	21.1 ± 3.2	< 0.001
ACL-RSI Score	91.4 ± 5.6	76.8 ± 8.5	65.2 ± 9.3	< 0.001

ACL-RSI Anterior cruciate ligament return-to-sport after injury scale, TSK-11 Tampa scale of kinesiophobia, SD Standard deviation

The revision ACL group reported higher fear-avoidance (TSK-11 = 21.1 ± 3.2) and lower psychological readiness (ACL-RSI = 65.2 ± 9.3) compared with the primary ACL and control groups (p < 0.001 for both measures). These differences correspond to large between-group effects (η² = 0.41 and 0.44, respectively).

As shown in Table 6, moderate-to-strong correlations were identified between neurophysiological, cognitive, and psychological variables. Higher theta/beta ratios were positively correlated with longer reaction times (r = 0.61, p < 0.001) and greater kinesiophobia (r = 0.58, p = 0.001), and negatively correlated with ACL-RSI scores (r = − 0.50, p = 0.003).

Table 6.

Correlation between EEG, reaction Time, and psychological measures (n = 60)

Variables	Theta/Beta Ratio	Reaction Time	ACL-RSI	TSK-11
Theta/Beta Ratio	1	r = 0.61, p < 0.001	r = − 0.50, p = 0.003	r = 0.58, p = 0.001
Reaction Time	–	1	r = − 0.45, p = 0.007	r = 0.53, p = 0.002
ACL-RSI	–	–	1	r = − 0.68, p < 0.001
TSK-11	–	–	–	1

EEG Electroencephalography, RT Reaction time, ACL-RSI Return-to-sport scale, TSK-11 Tampa scale of kinesiophobia

Similarly, longer reaction times were associated with higher TSK-11 and lower ACL-RSI scores (p < 0.01 for all comparisons).

Discussion

In this study, a multidimensional evaluation of neurophysiological, cognitive, and psychological outcomes was conducted in athletes following anterior cruciate ligament reconstruction, with a particular focus on comparing primary and revision surgery groups to healthy controls. The results demonstrated significant differences across all domains—including frontal EEG theta/beta ratios, visual reaction times, and psychological scale scores—underscoring the complex and widespread impact of ACL injuries beyond structural and biomechanical disruption.

One of the most prominent findings was the progressive increase in the frontal theta/beta ratio from the control group to the primary ACL group and, most notably, the revision ACL group. Although the theta/beta ratio is a useful proxy for attentional control, it is not entirely specific and may also reflect nonspecific states such as fatigue, arousal, caffeine intake, or emotional stress—factors that could not be fully standardized in the current protocol. Nonetheless, the consistent pattern across three experimental conditions suggests a graded alteration in attentional engagement and frontal cortical efficiency that appears to intensify with repeated surgical intervention. These findings align with prior electrophysiological evidence indicating compensatory or maladaptive cortical reorganization after ACL injury, particularly within regions involved in motor planning and executive control [22, 32, 33]. Collectively, they support the emerging view that ACL injuries are not solely musculoskeletal events but part of a broader neuromusculoskeletal continuum, where peripheral structural damage and central neural adaptation interact reciprocally.

In line with the EEG findings, athletes in the revision group exhibited significantly prolonged reaction times compared to both the primary ACL and control groups. Given that only a simple visual reaction test with five trials was used, the current findings should be interpreted as reflecting basic neuromotor processing rather than complex sport-specific response capacity. However, even this simplified paradigm revealed measurable slowing, suggesting that central processing speed and sensorimotor coupling may remain compromised after multiple surgeries. Future studies should include more ecologically valid paradigms—such as choice reaction or dual-task conditions—to better capture sport-relevant cognitive-motor integration.

Psychological readiness, as measured by the ACL-RSI scale, and kinesiophobia, as measured by the TSK-11, further distinguished the groups. Athletes in the revision group reported lower confidence, greater emotional distress, and higher fear of reinjury compared to those in the primary group, with both surgical groups scoring significantly worse than healthy controls. These findings are consistent with previous research demonstrating that psychological factors—especially fear of movement and perceived readiness—are critical determinants of return-to-sport outcomes [26, 34]. However, as the current study did not directly evaluate actual return-to-sport rates or physical performance outcomes, such inferences should be considered conceptual rather than empirical. The results nevertheless emphasize that even after satisfactory physical recovery, psychological barriers may persist, particularly in revision cases where previous surgical failure may undermine self-efficacy and resilience.

From a broader perspective, these results reinforce the notion that cognitive and psychological domains should be integrated into post-ACL rehabilitation frameworks. Cognitive functions such as attention, inhibitory control, and working memory have been increasingly linked to injury susceptibility and motor control efficiency in athletes [14, 35]. Accordingly, interventions targeting both neuromotor and executive function domains—through neurofeedback, cognitive-motor dual-task training, or mental resilience programs—may enhance long-term recovery and reduce reinjury risk.

Collectively, the present findings advocate for a multidisciplinary and neuromusculoskeletal-based rehabilitation paradigm that extends beyond structural restoration. Such an approach integrates cortical function, motor performance, and psychological state, aligning with the growing evidence supporting neurocognitive and psychosocial assessment as adjuncts to physical recovery monitoring [36].

Limitations

Despite its novel and multidisciplinary approach, this study has several limitations that should be acknowledged.First, the cross-sectional design precludes the ability to establish causal relationships between ACL injury, cortical activity, psychological readiness, and motor performance. Longitudinal studies are needed to evaluate how these parameters evolve over time and in response to rehabilitation interventions.

Second, although the sample size was adequately powered for group comparisons, the study population consisted exclusively of young adult male athletes, limiting the generalizability of the findings to female athletes or older populations. Future studies should include sex as a biological variable rather than an exclusion criterion, as hormonal cycles and sex-based neural plasticity may influence both EEG patterns and rehabilitation outcomes [37].

Third, while the theta/beta ratio is a widely accepted marker of attentional control, it may be influenced by various uncontrolled factors such as fatigue, sleep quality, or transient stress levels. Although participants were tested under standardized conditions, subtle variations in alertness or emotional arousal could still contribute to EEG variability. Similarly, the computer-based reaction time task provides valuable insight into sensorimotor processing, but it does not fully represent the dynamic and context-specific decision-making demands of athletic competition.

Fourth, although validated questionnaires (TSK-11 and ACL-RSI) were used to assess psychological variables, self-report measures are inherently subject to response bias and may not fully capture the complexity of emotional and cognitive responses in return-to-sport scenarios.

Finally, the revision ACL group may have exhibited greater heterogeneity in terms of surgical history, graft type, and rehabilitation exposure, which could have influenced outcome variability. These factors were descriptively reported but not statistically modeled due to limited subgroup size. Moreover, as highlighted by prior longitudinal research, complete neuromotor and cognitive recovery may extend well beyond the six-month post-rehabilitation period used as an inclusion criterion [8, 38].

Conclusion

In conclusion, the present study provides evidence that ACL injuries—particularly in the context of revision surgery—are associated with measurable alterations in attention-related cortical activity, neuromotor response speed, and psychological readiness. The integration of EEG analysis, reaction time testing, and psychological profiling offers a novel and comprehensive framework for evaluating post-surgical recovery. While causality cannot be inferred, the observed associations highlight the potential value of including neurocognitive and psychological metrics in rehabilitation and RTS decision-making. Future longitudinal and interventional studies are warranted to clarify temporal dynamics and establish targeted strategies for optimizing outcomes through personalized, interdisciplinary rehabilitation programs.

Abbreviations

ACL

Anterior Cruciate Ligament

ACLR

Anterior Cruciate Ligament Reconstruction

ACL-RSI

Anterior Cruciate Ligament: Return to Sport after Injury Scale

BMI

Body Mass Index

CNS

Central Nervous System

EEG

Electroencephalography

FFT

Fast Fourier Transform

Hz

Hertz

RT

Reaction Time

SD

Standard Deviation

TSK-11

Tampa Scale of Kinesiophobia

Authors’ contributions

HBK and VU contributed to study conception, design, data collection, and manuscript writing. ZOK and MA were responsible for EEG protocol development, electrophysiological analysis, and technical supervision. SA and SS assisted with orthopedic evaluation and participant recruitment. SAK contributed to psychological assessments and interpretation of psychometric results. MK was responsible for reaction time testing and statistical analysis. All authors (HBK, ZOK, SA, MA, SS, SAK, MK, VU) reviewed and approved the final manuscript and agreed to be accountable for all aspects of the work.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Data availability

The datasets generated and/or analyzed during the current study are available from the corresponding author (VU) on reasonable request.

Declarations

Ethics approval and consent to participate

The study was conducted in accordance with the ethical standards of the Declaration of Helsinki. Ethical approval was obtained from the Düzce University Non-Interventional Clinical Research Ethics Committee (Approval No: 2025/177, Date: 16/06/2025). All participants provided written informed consent prior to data collection.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.