GNRB® Knee Arthrometer: Inter- and Intra-observer Reliability and Learning Curve.

Background Diagnosing anterior cruciate ligament rupture is challenging, particularly due to the subjective nature of clinical laxity assessments. Objective evaluation methods are necessary for consistency and publication in clinical research. This study aims to assess the reproducibility of the GNRB® knee arthrometer (GeNouRoB, Laval, France) across different examiners and to examine the associated learning curve for a junior examiner. Methods Anterior translation measurements were conducted on 20 healthy knees using the GNRB arthrometer. Two examiners, a senior and a junior, performed the measurements independently and were blinded to each other's results. Measurements were taken at two different push forces (134 N and 200 N). The study evaluated inter- and intra-observer reproducibility using Cohen's kappa coefficient and the intraclass correlation coefficient (ICC). The junior examiner also performed a third series of measurements to assess the learning curve. Results The senior examiner demonstrated excellent reproducibility with an ICC greater than 0.75 for all measurements. The junior examiner's reproducibility varied from fair to good, with an ICC ranging from 0.45 to 0.75. Inter-observer reproducibility between the senior and junior examiners was excellent (ICC >0.75). Notably, the junior examiner's reproducibility improved to an excellent level (ICC >0.75) during the second series of measurements. Conclusion The GNRB system provides a reproducible method for evaluating anterior knee laxity across different examiners. A learning curve of approximately 20 knees is sufficient for a junior examiner to achieve statistically excellent reproducibility.