Psychological and Physiological Parameters for Return-to-sport After ACL Reconstruction (ACL-RTS)

Long-term Correlation of Functional and Psychological Parameters for the Return-to-sport Decision After Anterior Cruciate Ligament Reconstruction

Injuries to the anterior cruciate ligament are common and are usually treated with reconstruction and subsequent rehabilitation. Many people succeed in return to sport (RTS), but not to the original level. Muscle strength factors can be assessed using isokinetic strength measurements, while the psychological readiness to return to sport can be assessed using the Anterior Cruciate Ligament-Return to Sport after Injury (ACL-RSI) questionnaire. In this study, isokinetic strength testing and psychological testing with the ACL-RSI questionnaire 1 to 4 years after ACL reconstruction will be assessed. The study will be conducted at the Institute of Physical Medicine & Rehabilitation at the Kepler University Hospital. The Biodex System Pro™, a medical device for measuring and training muscle strength, will be used for the isokinetic measurements. The research question is as follows: Is there a correlation between the results of the ACL RSI questionnaire and the results of isokinetic strength testing on the Biodex System 4 Pro™ in test subjects following ACL reconstruction?

Study Overview

• Status: Completed
• Conditions: ACL Reconstruction

• Study Type: Observational
• Enrollment (Actual): 30

Contacts and Locations

Study Locations

• Austria
  • Linz, Austria, 4021
    • Kepler University Clinic, Dept. of Physical Medicine & Rehabilitation

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

• Sampling Method: Probability Sample

Study Population

Physically active adults who underwent unilateral ACL reconstruction 1 to 4 years ago

Description

Inclusion Criteria:

• Primary unilateral ACL reconstruction 1 to 4 years prior testing
• Physically active
• 18-50 years
• Medical approval for maximum loads

Exclusion Criteria:

• Bilateral Knee injury
• Pregnancy
• Acute pain (VAS ≥ 3)
• Extremely limited mobility
• Extreme joint instability
• Acute injuries
• Inflammation
• Fever

Study Plan

How is the study designed?

Number of groups / cohorts

1

Cohorts and Interventions

Group / Cohort
Participants after ACL reconstruction; 1 to 4 years after ACL reconstruction, age: 18 - 50 years, physically active

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Peak torque (Nm) - Isokinetic dynamometry (Biodex System 4)	The isokinetic dynamometer measures concentric strength in extension and flexion. Isokinetic strength testing at a ROM (range of motion) of 0-90° knee flexion at 3 different speeds. Test protocol at angular velocities of 60°/sec, 180°/sec and 240°/sec.	Day 1 (1 to 4 years after ACL reconstruction)
ACL-RSI questionnaire (Anterior Cruciate Ligament-Return to Sport after Injury)	The ACL-RSI is a measure of psychological readiness to return to sport. It contains 12 questions and examines 3 components related to readiness to return to sport: emotions (5 questions), confidence in one's own performance (5 questions) and risk assessment (2 questions). The questions relate to the psychological effects of returning to sport. The respondents answer each question by giving their assessment in steps of ten on a Likert scale from 0 to 100 points. Low scores indicate a negative psychological assessment and high scores indicate a positive psychological assessment. The cut-off value for distinguishing between returnees and non-returnees is 51.3 points. A German version of the questionnaire is used.	Day 1 (1 to 4 years after ACL reconstruction)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Isokinetic dynamometry (Biodex System 4)	The isokinetic dynamometer measures concentric strength in extension and flexion including following parameters: Average peak torque (Nm), time to peak torque (sec), angle of peak torque (deg), torque at 30°, torque at 0.18 seconds, max. repetitions to total work, work/body weight, total work, work first third, work last third, work fatique, avg. power, acceleration time (msec), ROM (range of motion, deg), agonist/antagonist ratio (%), hamstring/quadriceps (H/Q) ratio, LSI (limb symmetry index) Isokinetic strength testing at a ROM of 0-90° knee flexion at 3 different speeds. Test protocol at angular velocities of 60°/sec, 180°/sec and 240°/sec.	Day 1 (1 to 4 years after ACL reconstruction)
Sports activity	Sports activity before and after surgery in minutes/week	Day 1

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Time since ACL surgery	Time in months since ACL surgery	Day 1
Height	Height of the participant in cm	Day 1
Weight	Weight of the participant in kg	Day 1
Body Mass Index	Relation of body weight to the square of body height	Day 1 (1 to 4 years after ACL reconstruction)
Age	Age of the participant in years	Day 1

Collaborators and Investigators

• Sponsor: Johannes Kepler University of Linz
• Collaborators: University of Salzburg

Study record dates

Study Major Dates

• Study Start (Actual): April 16, 2025
• Primary Completion (Actual): September 1, 2025
• Study Completion (Actual): December 30, 2025

Study Registration Dates

• First Submitted: April 16, 2025
• First Submitted That Met QC Criteria: November 21, 2025
• First Posted (Actual): December 2, 2025

Study Record Updates

• Last Update Posted (Actual): April 20, 2026
• Last Update Submitted That Met QC Criteria: April 15, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Dynamometry; ACL reconstruction; ACL tear; ACL rupture; Return to sport
• Additional Relevant MeSH Terms: Wounds and Injuries; Leg Injuries; Knee Injuries; Anterior Cruciate Ligament Injuries
• Other Study ID Numbers: Kepler Universitätsklinikum /

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No