Measuring Knee Laxity and Pivot Shift in ACL-Deficient Patients

Objective Quantification of Knee Laxity Using a Robotic Knee Testing System and Correlation With Clinical Pivot Shift Grade in ACL-Deficient Patients

The goal of this observational study is to learn whether the Robotic Knee Testing system can measure knee looseness in adults with an anterior cruciate ligament, or ACL, tear.

The main question it aims to answer is whether measurements from the Robotic Knee Testing system are related to the doctor's pivot shift exam grade.

Participants will complete one study visit before ACL reconstruction. During the visit, both knees will be tested in the Robotic Knee Testing system. Researchers may also review existing medical information and imaging.

Study Overview

• Status: Not yet recruiting
• Conditions: Anterior Cruciate Ligament (ACL) Tear

Detailed Description

This study includes two parts. In Phase 1, researchers will adjust the Robotic Knee Testing system settings to identify testing conditions that are safe, tolerable, and able to reproduce knee motion similar to the pivot shift exam.

During Phase 1, the device will test how knee motion changes when the leg is placed in different positions. Researchers will evaluate whether tibial internal rotation and knee flexion angle change varus-valgus knee motion. They will also evaluate whether varus-valgus knee position and knee flexion angle change internal-external tibial rotation. These tests are intended to help identify device settings that may reproduce the coupled motion seen during a clinical pivot shift exam.

The robotic torque-motion curves will also be reviewed for abrupt changes, discontinuities, or "jumps." These findings may represent the knee moving from a stable position into an unstable position.

In Phase 2, participants will be tested using the finalized device settings from Phase 1. The device will apply controlled anterior-posterior, internal-external rotation, and varus-valgus movements while measuring knee motion in six degrees of freedom. Researchers will compare the robotic measurements with the pivot shift grade documented by the treating orthopedic surgeon.

When available, existing MRI or X-ray images may also be reviewed to evaluate whether knee bone structure is related to robotic laxity measurements or pivot shift severity. No additional imaging will be performed for this study.

• Study Type: Observational
• Enrollment (Estimated): 25

Contacts and Locations

• Study Contact: Name: Samantha J Beckley, PhD; Phone Number: 470-955-7069; Email: s.beckley@arthroresearch.com
• Study Contact Backup: Name: Shaun K Stinton, PhD; Email: s.stinton@arthroresearch.com

Study Locations

• United States
  • Georgia
    • Atlanta, Georgia, United States, 30324
      • Trailer
      • Contact: Samantha J Beckley, PhD; Phone Number: 470-955-7069; Email: s.beckley@arthroresearch.com

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Non-Probability Sample

Study Population

Study participants will be selected from patients being treated for ACL injury by orthopedic providers in the Atlanta metropolitan area. Participants will generally be identified through orthopedic clinic schedules, clinical referrals, or patients scheduled for ACL reconstruction.

Description

Inclusion Criteria:

• Adults aged 18-65 years
• Confirmed ACL tear by MRI or arthroscopic diagnosis
• Able to provide informed consent

Exclusion Criteria:

• Prior major surgery on the affected knee
• Multi-ligament knee injury
• Active infection or inflammatory arthropathy
• Inability to tolerate passive motion testing
• Pregnant or planning to become pregnant during the study period
• Unable to provide informed consent

Study Plan

How is the study designed?

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Clinician-graded pivot shift	Clinician-graded pivot shift from 0 to 3, obtained from the treating orthopedic surgeon's preoperative clinical exam and/or examination under anesthesia before ACL reconstruction.	Before ACL reconstruction, during the preoperative clinical exam and/or examination under anesthesia.
Association Between RKT Knee Motion Measurements and Clinician-Graded Pivot Shift Grade	Relationship between Robotic Knee Testing measurements of tibiofemoral motion and clinician-graded pivot shift grade from 0 to 3. RKT measurements may include tibial translation and rotation during robotic testing.	RKT testing at the preoperative study visit and pivot shift grading before ACL reconstruction

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
RKT Torque-Motion Hysteresis Curve Features	Torque-displacement and torque-rotation curves from robotic testing will be evaluated for features such as slope changes, curve area, discontinuities, or "jumps" that may reflect knee instability.	During RKT testing at the preoperative study visit before ACL reconstruction
Effect of Knee Position on RKT Motion Measurements	RKT measurements will be compared across different testing conditions, including tibial internal rotation angle, varus-valgus knee position, knee flexion angle, and preset torque thresholds, to identify settings associated with pivot-shift-like motion.	During RKT testing at the preoperative study visit before ACL reconstruction
Association Between Bone Morphology and Knee Instability Measurements	Existing MRI or X-ray images may be reviewed to assess bone morphology, including posterior tibial slope and femoral-tibial plateau geometry, and compare these measures with RKT measurements and pivot shift grade.	Existing imaging reviewed after enrollment and before data analysis

Collaborators and Investigators

• Sponsor: Arthroresearch LLC
• Investigators: Principal Investigator: Shaun K Stinton, PhD, Arthroresearch LLC

Study record dates

Study Major Dates

• Study Start (Estimated): July 7, 2026
• Primary Completion (Estimated): July 1, 2027
• Study Completion (Estimated): July 1, 2027

Study Registration Dates

• First Submitted: June 30, 2026
• First Submitted That Met QC Criteria: June 30, 2026
• First Posted (Actual): July 7, 2026

Study Record Updates

• Last Update Posted (Actual): July 7, 2026
• Last Update Submitted That Met QC Criteria: June 30, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: anterior cruciate ligament; knee instability; pivot shift; robotic knee testing
• Additional Relevant MeSH Terms: Wounds and Injuries; Lacerations
• Other Study ID Numbers: 15940

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