May 2023, The Knee 42(8, Supplement):373-381

DOI: 10.1016/j.knee.2023.03.017

Théo Cojean, Cécile Batailler, Henri Robert, Laurence Cheze

Background: Accurate diagnosis of anterior cruciate ligament (ACL) injury is not always obtained with magnetic resonance imaging (MRI). Other tools, such as the GNRB! arthrometer, help to accurately identify the type of ACL tear. The aim of this study was to show that the GNRB! could be a relevant complementary solution to MRI in ACL injury detection. Methods: A prospective study performed between 2016 and 2020 included 214 patients who had undergone knee surgery. The study compared sensitivity/specificity pairs of MRI and the GNRB! at 134 N to detect healthy ACL, partial, and complete ACL tears. Arthroscopies were the ‘gold standard’. Forty-six patients had a healthy ACL with associated knee lesions, 168 patients had ACL tears where 107 were complete tears and 61 were partial tears.

Results: For healthy ACL, MRI scored 100% for sensitivity (SE) and 95% for specificity (SP), and the GNRB! scored SE 95.65% and SP 97.5% at 134 N. For complete ACL tears, MRI scored 80.81% for sensitivity (SE) and 64.49% for specificity (SP), and the GNRB! scored SE 77.78% and SP 85.98% at 134 N. For partial tears, MRI scored SE 29.51% and SP 88.97%, and the GNRB! scored SE 73.77% and SP 85.52% at 134 N.

Conclusion: GNRB! sensitivity and specificity were equivalent to those of MRI for healthy ACL and complete ACL tear detection. However, MRI had some difficulty in detecting partial ACL tears compared with the GNRB! which showed better sensitivity.


  • GNRB is at least as effective as MRI in complete ACL tear and healthy ACL detection.
  • GNRB shows an interest in detecting partial ACL tears compared to MRI.
  • Combining GNRB and MRI can improve the diagnosis of ACL tears.
  • GNRB brings a dynamic vision of the biomechanical behavior of the ligament.