ACL-Return to Sport after Injury scale

1. Abstract

The ACL-Return to Sport after Injury (ACL-RSI) scale is a specialized, patient-reported psychometric instrument designed to quantify the psychological readiness of athletes returning to sports participation following anterior cruciate ligament (ACL) reconstruction. Historically, orthopedic and physical therapy paradigms evaluated return-to-sport (RTS) clearance through mechanical stability, muscle strength symmetry, and objective functional movement assays. However, high rates of secondary injury and surprisingly low rates of resumption of pre-injury athletic activity underscored an unaccounted-for dimension: cognitive and affective inhibition. Developed by Kate E. Webster, Julian A. Feller, and Christina Lambros in 2007, the ACL-RSI directly addresses this discrepancy across three primary dimensions: emotions, confidence in performance, and risk appraisal.

Comprising 12 items administered via a 10 cm visual analogue scale (VAS) ranging from 0 to 100, the instrument yields a cumulative percentage score where higher values reflect superior psychological readiness. Psychometric evaluations demonstrate exceptional internal consistency, yielding a Cronbach's alpha of 0.92 in the original validation cohort of 220 post-operative athletes. Construct and known-groups validity analyses reveal marked, statistically significant differentiations between athletes who successfully resume competitive athletic engagement and those who voluntarily curtail or cease sports involvement due to non-physical barriers (p < 0.001). Subsequent cross-cultural adaptations and structural validations have consolidated its international stature as an indispensable biopsychosocial measurement tool, aiding clinicians, orthopedic surgeons, and sports psychologists in pinpointing athletes requiring targeted cognitive-behavioral or exposure-based rehabilitation interventions.

2. Keywords

ACL-Return to Sport after Injury scale, ACL-RSI, anterior cruciate ligament reconstruction, psychological readiness, return to sport, fear of reinjury, athletic rehabilitation, self-efficacy, kinesiophobia, sports psychology, sports injury assessment, psychometrics

3. Authors

The ACL-Return to Sport after Injury scale was conceptualized and validated by a distinguished multidisciplinary research team based at the Musculoskeletal Research Centre at La Trobe University in Melbourne, Australia:

• Kate E. Webster, Ph.D. — School of Allied Health, Human Services and Sport, Musculoskeletal Research Centre, La Trobe University, Melbourne, Victoria 3086, Australia. Email: [email protected]. Dr. Webster is an internationally acknowledged authority in sports medicine biomechanics, orthopedics, and the psychological sequelae of traumatic knee injuries.
• Julian A. Feller, FRACS — Musculoskeletal Research Centre, La Trobe University, and OrthoSport Victoria, Epworth Healthcare, Richmond, Victoria, Australia. Mr. Feller is an internationally prominent orthopedic knee surgeon renowned for longitudinal clinical trials on ACL graft selection, surgical biomechanics, and long-term joint morbidity.
• Christina Lambros, B.Phty (Hons) — Musculoskeletal Research Centre, School of Physiotherapy, La Trobe University, Melbourne, Victoria, Australia. Clinical physical therapist and musculoskeletal rehabilitation researcher.

4. Purpose

The primary purpose of the ACL-Return to Sport after Injury (ACL-RSI) scale is to furnish an empirical, standardized, and sensitive metric that assesses the complex psychological barriers impeding an athlete's transition from physical clearance back into competitive sporting environments. In traditional orthopedic sports medicine, successful post-operative recovery following anterior cruciate ligament reconstruction (ACLR) was judged nearly exclusively through biomedical markers, including graft integrity verified via Lachman tests or arthrometric laxity metrics, limb symmetry indices (LSI) derived from isokinetic dynamometry, and lower-extremity functional performance battery assays (such as single, triple, and crossover hop tests). Despite reaching physical benchmarks indicative of clinical recovery, systematic reviews consistently indicated that only approximately 55% to 65% of athletes successfully returned to their pre-injury competitive levels, and as few as 80% returned to any form of physical recreation.

Extensive clinical observation and qualitative inquiries revealed that this persistent discrepancy was overwhelmingly driven by psychological inhibitors rather than biological deficits. Patients cited profound apprehension regarding joint re-rupture, chronic preoccupation with limb vulnerability, alienation from athletic identity, and an inability to trust the operated knee during reactive, non-linear sporting tasks. The ACL-RSI was engineered specifically to systematically measure this unobservable internal landscape. By providing sports medicine clinicians, physical therapists, and sports psychologists with a continuous score representing readiness, the instrument fulfills vital diagnostic, prognostic, and evaluative functions.

Clinically, the ACL-RSI serves as a screening mechanism to identify athletes who, despite displaying satisfactory physical recovery, harbor hidden psychosocial impediments that place them at heightened risk of poor long-term function or maladaptive movement compensations. In contemporary clinical algorithms, low psychological readiness has been empirically linked to biomechanical hesitations, altered lower-extremity neuromuscular control, and elevated risks of secondary ipsilateral graft failure or contralateral ACL tear upon athletic resumption. Consequently, the ACL-RSI establishes an empirical baseline that guides targeted cognitive-behavioral strategies, progressive biofeedback, and graded exposure therapy prior to full unrestricted sports clearance. Within academic research, the instrument provides an indispensable standardized outcome endpoint for comparing clinical rehabilitation pathways, testing psychological interventions, and characterizing long-term trajectory profiles across diverse athletic cohorts.

5. Psychological Construct

The overarching construct quantified by the ACL-RSI is psychological readiness to return to sport following primary or revision ACL reconstruction. Psychological readiness is not a monolithic affective state; rather, it is a multifaceted cognitive-affective construct characterized by three distinct yet deeply intertwined latent domains: emotions, confidence in performance, and risk appraisal.

Emotions (Affective Responses)

The emotional domain encompasses the subjective, affect-laden responses triggered by the prospect of re-entering competitive sports. Traumatic knee injuries represent profound psychological disruptions, frequently inducing reactive states of nervousness, heightened situational anxiety, generalized frustration, and chronic kinesiophobia (fear of movement or reinjury). Within the ACL-RSI, affective items capture how intensely an athlete experiences internal tension or emotional apprehension when contemplating unrestricted athletic play. For example, an athlete may possess intact structural biomechanics but experience debilitating autonomic arousal or distress upon imagining a sudden cut, deceleration, or physical collision with an opponent. Chronic frustration regarding the extended timeline of physical rehabilitation and the persistent cognitive vigilance required to protect the joint further characterizes this dimension.

Confidence in Performance (Self-Efficacy)

The confidence dimension evaluates an individual's contextual self-efficacy regarding their knee's functional capacity and their personal competence to execute demanding motor patterns without catastrophic mechanical collapse. Grounded largely in social cognitive formulations, this domain probes whether the patient genuinely believes their operated knee can withstand multi-planar torsional stress ("holding up to demands") and remain stable without giving way. Crucially, it extends past mechanical belief into cognitive flow and attentional focus: high confidence is signified by an athlete's capacity to participate automatically, spontaneously, and fluidly without allocating conscious working memory to monitor, protect, or hesitate on the operated limb. Individuals with low scores in this domain demonstrate cognitive hyper-vigilance, constantly scanning the joint for internal proprioceptive sensations of vulnerability.

Risk Appraisal (Cognitive Evaluation of Consequence)

The risk appraisal domain delineates the subjective cognitive probability and severity that an athlete assigns to negative future events, specifically sustaining a secondary ligament tear. While athletic participation naturally involves an inherent degree of baseline physical danger, post-operative athletes often engage in cognitive distortions, catastrophizing the likelihood of reinjury. This dimension quantifies the degree to which perceived risk acts as an absolute behavioral deterrent. Athletes weighing this risk consider not only the physical trauma of structural reinjury but also the heavy psychosocial costs associated with repeating the arduous 9-to-12-month rehabilitation odyssey, undergoing repeat surgical reconstructive procedures, experiencing professional or recreational identity disruption, and suffering prolonged occupational or athletic loss.

6. Theoretical Framework

The architectural foundation of the ACL-RSI synthesizes several prominent paradigms from health psychology, motor learning, and sports traumatology, notably Albert Bandura's Social Cognitive Theory, the Biopsychosocial Model of injury recovery (Brewer et al., 2002), the Cognitive Appraisal Model of Coping with Athletic Injury (Wiese-Bjornstal et al., 1998), and the Fear-Avoidance Model of Musculoskeletal Pain (Vlaeyen & Linton, 2000).

Social Cognitive Theory and Task-Specific Self-Efficacy

Bandura posited that behavior is heavily dictated by self-efficacy beliefs—an individual's confidence in their ability to execute specific courses of action necessary to manage prospective situations. In the context of knee trauma, Bandura's theoretical tenets suggest that physiological capabilities (such as quadriceps hypertrophy or peak torque) are mediated by perceived capability. If an athlete does not hold efficacious beliefs regarding their knee's integrity during high-speed agility maneuvers, avoidance behavior ensues regardless of biological readiness. The ACL-RSI measures efficacy across Bandura's proposed informational channels: enactive mastery experiences (recurrent successful rehabilitation milestones), vicarious experiences (observing peers successfully navigate return-to-sport), and physiological/affective states (interpreting joint crepitus or rehabilitation soreness as non-threatening rather than catastrophic).

Cognitive Appraisal and the Biopsychosocial Paradigm

Wiese-Bjornstal and colleagues conceptualized athletic injury recovery as a continuous, dynamic cognitive appraisal loop. Following injury and subsequent reconstructive surgery, personal factors (e.g., personality, athletic identity, coping styles) and situational factors (e.g., sport type, competitive level, coaching pressures) interact to produce cognitive appraisals. These cognitive assessments continuously shape emotional responses (fear, depression, mood disturbance) and behavioral responses (rehabilitation adherence, effort, withdrawal). The ACL-RSI operationalizes the cognitive and affective nodes within this dynamic model, recognizing that an athlete's appraisal of threat versus challenge directly dictates their readiness to resume competitive sports.

The Fear-Avoidance Model of Musculoskeletal Rehabilitation

Originally formulated within chronic low back pain paradigms, the Fear-Avoidance Model delineates how individuals who catastrophize pain or structural sensations enter a vicious spiral of pain-related fear, kinesiophobia, hyper-vigilance, and prolonged behavioral avoidance, leading to physical deconditioning and heightened psychological disability. Conversely, individuals who appraise physical sensations as non-threatening engage in confrontational, active exposure pathways leading to recovery. The ACL-RSI captures elements of this model by operationalizing how pervasive fears of structural re-injury disrupt an athlete's psychological state, precipitating motor avoidance strategies, guarded kinematics, and premature athletic retirement.

7. Validity

The psychometric validity of the ACL-RSI scale has been thoroughly established through numerous rigorous empirical investigations across diverse global athletic cohorts.

Known-Groups and Construct Validity

During its initial validation by Webster, Feller, and Lambros (2007), known-groups validity was robustly confirmed among 220 athletic subjects. The investigators hypothesized that individuals who had determined not to return to competitive sports would exhibit significantly lower psychological scores than those actively engaged in sport or preparing for imminent re-entry. In alignment with hypotheses, athletes who had ceased sports participation scored significantly lower across all dimensions (mean score: 46.6 ± 23.9) compared to athletes who successfully returned to their pre-injury level of competition (mean score: 71.4 ± 19.3; p < 0.001). This divergence proved the instrument's power to distinguish between behavioral outcomes driven by psychological readiness.

Predictive and Discriminant Validity

Subsequent prospective cohort investigations demonstrated strong predictive validity. Webster and Feller (2018) showed that ACL-RSI scores captured at 6 and 12 months post-operatively significantly predicted which athletes would return to their pre-injury competitive sport at 2 to 3 years post-surgery. A baseline cutoff threshold of approximately 56 to 60 points was identified across multiple receiver operating characteristic (ROC) curve analyses; patients scoring below this cutoff exhibited markedly lower probabilities of ever regaining pre-injury competition levels. Furthermore, research by McPherson et al. (2019) demonstrated an inverse, paradoxical relationship between psychological readiness and secondary injury risk: younger athletes with exceptionally high ACL-RSI scores (>75-80 points) returning very rapidly to high-impact cutting sports demonstrated higher rates of secondary graft or contralateral tear, highlighting the clinical necessity of matching high psychological readiness with objective physical motor competency.

Convergent and Concurrent Validity

The scale demonstrates moderate-to-strong correlations with conceptually aligned patient-reported outcome measures (PROMs). The ACL-RSI correlates moderately and positively with the International Knee Documentation Committee (IKDC) Subjective Knee Form (r = 0.58 to 0.68) and the Lysholm Knee Scoring Scale (r = 0.45 to 0.55). Crucially, the scale exhibits robust inverse correlations with the Tampa Scale for Kinesiophobia (TSK-11) (r = -0.60 to -0.73) and the Pain Catastrophizing Scale (PCS), confirming that lower scores capture heightened movement-related terror and catastrophizing cognitions while preserving uniqueness specific to athletic demands.

8. Reliability

The ACL-RSI exhibits robust internal consistency and test-retest reproducibility across multiple linguistic adaptations and clinical settings.

Internal Consistency

In the seminal psychometric validation study conducted by Webster et al. (2007), internal consistency reliability for the 12-item instrument was calculated using Cronbach's alpha coefficient, resulting in an exceptionally strong α = 0.92. This coefficient comfortably surpasses the recognized standard criterion of 0.80 for group-level research and exceeds the stringent 0.90 threshold required for high-stakes individual patient clinical decision-making. Corrected item-total correlations across the 12 items ranged between 0.61 and 0.82, establishing that every single question contributes meaningful variance to the central construct of psychological readiness without excessive item redundancy.

Test-Retest Reliability and Measurement Error

Evaluation of temporal stability across repeated administrations indicates strong test-retest reproducibility. When administered over a 2- to 7-day interval in clinically stable cohorts prior to sports resumption, the intra-class correlation coefficient (ICC_2,1) consistently ranges from 0.89 to 0.95 across international validation cohorts (e.g., French, Swedish, German, Spanish, and Japanese adaptations). Studies evaluating measurement precision establish a Standard Error of Measurement (SEM) ranging from 3.5 to 5.2 points on the 100-point scale. The Minimal Detectable Change at the 95% confidence level (MDC₉₅) is consistently established between 9.7 and 14.4 points. This indicates that a change of approximately 10 points or more over time represents genuine psychological progression beyond measurement noise.

9. Factor Analysis

The underlying dimensionality and latent structural composition of the ACL-RSI scale have been rigorously scrutinized using both Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA).

Exploratory Factor Analysis (EFA)

In the initial scale construction phase by Webster et al. (2007), an exploratory factor analysis using principal components analysis with varimax rotation was executed on the 12 items. The analysis revealed a three-factor solution accounting for approximately 68.5% of the cumulative total variance:

• Factor 1: Emotions — Comprising items 1, 2, 3, 4, and 5 (accounting for the largest component of variance, ~48%), capturing affective states of nervousness, worry, frustration, and fear of reinjury.
• Factor 2: Confidence in Performance — Comprising items 6, 7, 8, 9, and 10 (~12.5% of variance), mapping cognitive self-efficacy regarding knee stability, competitive competence, and unconstrained motor fluidity.
• Factor 3: Risk Appraisal — Comprising items 11 and 12 (~8.0% of variance), isolating the cognitive probability of reinjury and the daunting contemplation of recurrent surgery.

Confirmatory Factor Analysis (CFA) and Structural Debates

Subsequent structural evaluations in larger international populations have explored whether the ACL-RSI is best conceptualized as a multi-dimensional three-factor construct or an overarching unidimensional scale. Confirmatory factor analytic investigations (e.g., by Webster & Feller, 2018; Bouras et al., 2019) have shown that while the three-factor model demonstrates excellent fit indices (Comparative Fit Index [CFI] > 0.95, Tucker-Lewis Index [TLI] > 0.94, Root Mean Square Error of Approximation [RMSEA] < 0.06), the inter-factor correlations between the three latent factors are exceptionally high (typically r > 0.85). Consequently, a second-order unidimensional model (where all 12 items load on their respective first-order factors, which in turn load powerfully on a single overarching superordinate latent factor: "Psychological Readiness") exhibits exemplary structural and empirical fit. Item factor loadings systematically range from 0.65 to 0.88, demonstrating that total composite summation across the 12 items is psychometrically justified.

10. Instrument / Measurement Tool

The formal characteristics and administrative requirements of the measurement tool are structured as follows:

• Test Name: ACL-Return to Sport after Injury scale (ACL-RSI)
• Test Type: Patient-Reported Outcome Measure (PROM) / Self-report psychological readiness questionnaire
• Target Population: Athletes and physically active individuals who have undergone anterior cruciate ligament reconstruction (ACLR)
• Validated Age Cohort: Adolescents and adults aged 16 to 54 years
• Administration Format: Self-administered (paper-and-pencil or secure electronic web application)
• Completion Time: Approximately 3 to 5 minutes
• Number of Items: 12 items
• Response Scale: 12 items, 10 cm Visual Analogue Scale (VAS). Each question is accompanied by a continuous 100 mm horizontal line anchored with contrasting extreme endpoints (e.g., 0 = "Not confident at all" to 100 = "Fully confident"; 0 = "Extremely fearful" to 100 = "Not fearful at all").
• Scoring Methodology:
  • Each item is measured in millimeters from the left-hand anchor to the respondent's mark, yielding an item score from 0 to 100.
  • Positively and negatively phrased items are systematically oriented so that 100 points always represents the most positive, adaptive psychological readiness.
  • Scores across all 12 items are summed and divided by 12 to generate an aggregate total percentage score ranging between 0 and 100 points.
• Clinical Interpretative Thresholds:
  • < 56%: Low psychological readiness; high apprehension, high risk of voluntary sports abandonment or biomechanical hesitation.
  • 56% – 64%: Moderate psychological readiness; transitional stage warranting continued targeted rehabilitation.
  • ≥ 65%: High psychological readiness; indicative of mental preparedness to resume unrestricted athletic competition.

11. Permissions & Fee and Test Year

The ACL-Return to Sport after Injury scale was formally published in 2007 in the peer-reviewed medical journal Physical Therapy in Sport by Elsevier. The instrument was developed within an academic institution (La Trobe University) to advance evidence-based clinical practices in sports orthopedic rehabilitation.

For independent non-commercial academic research and routine individual clinical care, the ACL-RSI is widely accessible and utilized under fair-use scientific guidelines without mandatory licensing fees. Clinicians, physical therapists, and researchers are encouraged to cite the foundational publication (Webster, Feller, & Lambros, 2007) in all derived clinical documentation, presentations, and scholarly publications. For commercial software integration, proprietary electronic health record (EHR) systems, or multi-site clinical trial licensing, formal permission inquiries should be directed to the corresponding primary developer, Dr. Kate E. Webster, at the Musculoskeletal Research Centre, La Trobe University, Melbourne, Australia ([email protected]), or through the permissions portal of the original journal publisher, Elsevier.

12. References

• Bandura, A. (1997). Self-efficacy: The exercise of control. W. H. Freeman.
• Bouras, T., Thomeé, R., Ejerhed, L., & Kvist, J. (2019). Cross-cultural adaptation, validity, and reliability of the Swedish version of the ACL-RSI scale. Knee Surgery, Sports Traumatology, Arthroscopy, 27(9), 2990–2998. https://doi.org/10.1007/s00167-018-5332-9
• Brewer, B. W. (2001). Psychology of sport injury rehabilitation. In R. N. Singer, H. A. Hausenblas, & C. M. Janelle (Eds.), Handbook of sport psychology (2nd ed., pp. 787–809). John Wiley & Sons.
• Brewer, B. W., Andersen, M. B., & Van Raalte, J. L. (2002). Psychological aspects of sport injury rehabilitation: Toward a biopsychosocial approach. In D. L. Mostofsky & L. D. Zaichkowsky (Eds.), Medical aspects of sport and exercise (pp. 41–54). Fitness Information Technology.
• Feller, J. A., & Webster, K. E. (2003). A randomised comparison of patellar tendon and hamstring tendon anterior cruciate ligament reconstruction. The American Journal of Sports Medicine, 31(4), 564–573. https://doi.org/10.1177/03635465030310041501
• Kvist, J., Ek, A., Sporrstedt, K., & Good, L. (2005). Fear of re-injury: A hindrance for returning to sports after anterior cruciate ligament reconstruction. Knee Surgery, Sports Traumatology, Arthroscopy, 13(5), 393–397. https://doi.org/10.1007/s00167-004-0591-8
• McPherson, A. L., Feller, J. A., Hewett, T. E., & Webster, K. E. (2019). Psychological readiness to return to sport is associated with second anterior cruciate ligament injuries. The American Journal of Sports Medicine, 47(4), 857–862. https://doi.org/10.1177/0363546518825258
• Podlog, L., & Eklund, R. C. (2007). The psychological aspects of a return to sport following serious injury: A review of the literature from a self-determination perspective. Psychology of Sport and Exercise, 8(4), 535–566. https://doi.org/10.1016/j.psychsport.2006.07.008
• Smith, A. M., Scott, S. G., O'Fallon, W. M., & Young, M. L. (1990). Emotional responses of athletes to injury. Mayo Clinic Proceedings, 65(1), 38–50. https://doi.org/10.1016/S0025-6196(12)62108-9
• Thomeé, P., Währborg, P., Börjesson, M., Thomeé, R., Eriksson, B. I., & Karlsson, J. (2006). A new instrument for measuring self-efficacy in patients with an anterior cruciate ligament injury. Scandinavian Journal of Medicine & Science in Sports, 16(3), 181–187. https://doi.org/10.1111/j.1600-0838.2005.00472.x
• Vlaeyen, J. W., & Linton, S. J. (2000). Fear-avoidance and its consequences in chronic musculoskeletal pain: A state of the art. Pain, 85(3), 317–332. https://doi.org/10.1016/S0304-3959(99)00242-0
• Webster, K. E., & Feller, J. A. (2018). Development and validation of a short version of the Anterior Cruciate Ligament Return to Sport After Injury (ACL-RSI) scale. Orthopaedic Journal of Sports Medicine, 6(4), 2325967118763763. https://doi.org/10.1177/2325967118763763
• Webster, K. E., Feller, J. A., & Lambros, C. (2007). Development and preliminary validation of a scale to measure the psychological impact of returning to sport following anterior cruciate ligament reconstruction surgery. Physical Therapy in Sport, 9(1), 9–15. https://doi.org/10.1016/j.ptsp.2007.09.003
• Wiese-Bjornstal, D. M., Smith, A. M., Shaffer, S. M., & Morrey, M. A. (1998). An integrated model of response to sport injury: Psychological and sociological dynamics. Journal of Applied Sport Psychology, 10(1), 46–69. https://doi.org/10.1080/10413209808406377

13. Items of the Scale