Objective pivot-shift grading.
In your clinic. Patient-driven.
GATOR Pro is the first device to predict pivot-shift grade from a patient-performed sit-stand-sit — moving rotational laxity assessment out of the operating theatre and into the routine outpatient knee exam.
Anterior translation is quantifiable. The ligament is imageable. Pivot-shift grade has remained subjective.
The pivot shift remains the most specific clinical test for anterolateral rotational instability in ACL-deficient knees. Grade 2 or 3 instability is a recognised indication for adjunct lateral extra-articular tenodesis (LEAP) — yet inter-observer agreement at the Grade 2 threshold is κ = 0.06.
Existing quantitative methods — navigation, accelerometry, inertial systems — typically require an examiner-performed manoeuvre under general anaesthesia.That confines rotational laxity quantification to the perioperative window.
Three steps. One signed grade.
Patient performs a sit-stand-sit exercise
The patient rises from a chair and sits back down, a weight-bearing movement that loads the knee through the screw-home rotation arc disrupted in ACL-deficient knees.
GATOR tracks femur-on-tibia rotation
B-mode ultrasound bone-surface tracking, combined with inertial sensors, captures the subtle kinematic events of the screw-home mechanism — free from the skin-motion artefact that limits marker-based or inertial-only systems in patients.
ML classifier returns a pivot-shift grade
An XceptionTime classifier, trained on intraoperative ground-truth labels from the SGH cohort, outputs a 0–3 pivot-shift grade. Generalises to unseen patients with held-out AUC 0.89 for the LEAP-decision threshold.
Peer-reviewed feasibility evidence,
independently held out.
Singapore General Hospital cohort, 29 ACL-injured patients. Ground-truth pivot-shift grading by fellowship-trained orthopaedic sports surgeons under general anaesthesia.
Low- vs high-grade pivot-shift classification on a held-out patient cohort (SGH).
High-grade pivot-shift detection (Grades 2/3) on unseen patients.
Overall classification accuracy across the 6-patient held-out validation cohort.
In-clinic, awake patient, no EUA, no imaging suite required.
What lands in the report.
Peak external rotation
Maximum outward tibial rotation relative to the femur during the sit-to-stand cycle (°). Higher magnitudes indicate greater rotational capacity.
Peak internal rotation
Maximum inward tibial rotation during the movement cycle (°). Reduced magnitude on the affected side may indicate rotational restriction.
Total IE rotation ROM
Total internal-to-external rotation arc across the full sit-to-stand cycle. The single strongest predictor used by the ML pivot-shift model.
Screw-home magnitude
Terminal external tibial rotation as the knee approaches full extension — the physiological locking mechanism. Reduced screw-home on the affected side is a hallmark of ACL deficiency.
Rep-to-rep CV
Coefficient of variation across repeated sit-to-stand cycles. Higher CV reflects neuromuscular instability or compensatory strategies.
Pivot-shift grade equivalent
ML-derived 0–3 grade with a confidence score, trained on IMU + ultrasound data against ACL-intact and ACL-deficient reference cohorts. Held-out AUC 0.89 for low- vs high-grade classification.
IKDC subjective evaluation
Patient-reported score (/100) across symptoms, sports activity, and knee function — captured alongside the kinematic assessment.
Selected ultrasound frames
B-mode ultrasound bone-tracking frames from the session, attached to the signed report for surgeon review.
The people who used to feel for it.
Now they measure it.
From four practice settings — academic, private, sports medicine, rehab.
GATOR is an effective and informative assessment tool. It has helped me and my patients evaluate objectively the post-surgical recovery and progress, guiding us in the rehabilitation program.
GATOR could be used by many people in the clinic. Those performing arthroplasty and sports-medicine reconstructive surgery would find it useful in examining their outcomes.
As a physiotherapist, I am always looking for ways to quantify rehab — both for myself and so patients can see, simply and clearly, that they're on the road to recovery.
What clinicians ask first.
How does GATOR Pro grade pivot shift? +
Does this replace EUA pivot-shift testing? +
Is the device cleared for clinical use? +
How much training does a clinician or technician need? +
See it in your clinic.
A 30-minute clinical demonstration with one of our specialists. We bring the device. You see your own patients assessed.