Objective evaluation of anterior knee laxity; comparison of the KT-1000 and GNRB® arthrometers

Knee Surg Sports Traumatol Arthrosc. 2012 Nov;20(11):2233-8. doi: 10.1007/s00167-011-1869-2. Epub 2012 Jan 10.


Purpose: Accurate measurement of laxity after anterior cruciate ligament (ACL) rupture is usually performed with the KT-1000 arthrometer, and reproducibility and reliability are discussed. A new arthrometer, the GNRB(®), has been recently developed in an attempt to improve intra- and inter-examiner reproducibility. The aim of this diagnostic study was to evaluate the intra- and inter-examiner reproducibility of the GNRB(®) and the KT-1000.

Methods: Three protocols were designed to evaluate and compare the two arthrometers. Fifteen physiotherapists conducted tests on 15 subjects with healthy knees. The intra- and inter-reproducibility of the two tests were compared by analysis of variance and the F-test.

Results: Measure reproducibility was significantly worst with the KT-1000 than with the GNRB(®) (machine effect, P < 0.001) regardless of operator experience. There was no significant difference between experienced and inexperienced examiners with the GNRB(®) (no 'examiners effect'). Regardless of the machine, there was a 'side effect' with healthy knees.

Conclusion: This clinical study demonstrates the superior intra- and inter-examiner reproducibility of the GNRB(®) over the KT-1000. There appears to be some technological advantages to using the GNRB(®) including pressure control of the patella, accuracy of the displacement transducer, control of the load on the calf, and control of hamstring activity.

Level of evidence: Diagnostic study, Level I.

Publication types

  • Comparative Study
  • Evaluation Study

MeSH terms

  • Adult
  • Arthrometry, Articular / instrumentation*
  • Arthrometry, Articular / methods
  • Clinical Competence
  • Humans
  • Joint Instability / diagnosis*
  • Joint Instability / physiopathology
  • Knee Joint / physiopathology*
  • Male
  • Reproducibility of Results
  • Young Adult