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

April 15, 2026 updated by: Christian Mittermaier, Johannes Kepler University of Linz

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

Status

Indicates the current recruitment status or the expanded access status.
Completed

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Observational

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
30

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

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

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

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

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort

Group / Cohort

A group or subgroup of participants in an observational study that is assessed for biomedical or health outcomes.
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

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Peak torque (Nm) - Isokinetic dynamometry (Biodex System 4)
Time Frame: Day 1 (1 to 4 years after ACL reconstruction)

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)
Time Frame: Day 1 (1 to 4 years after ACL reconstruction)
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

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Isokinetic dynamometry (Biodex System 4)
Time Frame: Day 1 (1 to 4 years after ACL reconstruction)

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
Time Frame: Day 1
Sports activity before and after surgery in minutes/week
Day 1

Other Outcome Measures

Other Outcome Measures

For clinical trials, a planned measurement described in the protocol that is used to determine the effect of an intervention/treatment on participants. For observational studies, a measurement or observation that is used to describe patterns of diseases or traits, or associations with exposures, risk factors, or treatment. Types of outcome measures include primary outcome measure and secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Time since ACL surgery
Time Frame: Day 1
Time in months since ACL surgery
Day 1
Height
Time Frame: Day 1
Height of the participant in cm
Day 1
Weight
Time Frame: Day 1
Weight of the participant in kg
Day 1
Body Mass Index
Time Frame: Day 1 (1 to 4 years after ACL reconstruction)
Relation of body weight to the square of body height
Day 1 (1 to 4 years after ACL reconstruction)
Age
Time Frame: Day 1
Age of the participant in years
Day 1

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Johannes Kepler University of Linz

Collaborators

Collaborators

An organization other than the sponsor that provides support for a clinical study. This support may include activities related to funding, design, implementation, data analysis, or reporting.
University of Salzburg

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
April 16, 2025

Primary Completion (Actual)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
September 1, 2025

Study Completion (Actual)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
December 30, 2025

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
April 16, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 21, 2025

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
December 2, 2025

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
April 20, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
April 15, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
April 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant 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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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