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Variability and intertester reliability of the KT-1000 knee ligament arthrometer

1 May 1992


With the expansion of innovative thinking in the growing field of physical therapy, clinical orthopaedic tests that were once subjectively analyzed can now be objectively measured. One example of this type of technology is the KT-1000 knee ligament arthrometer which measures the amount of tibial displacement in the anterior or posterior plane in millimeters, thereby quantifying the amount of anterior and posteriorcruciate laxities, respectfully. In order to analyze the KT-1000's clinical usefulness, this study compared the mean anterior displacement of normal subjects as examined by novice experimenters with means previously reported in the literature. A novice tester was defined as one with one houris instruction by an experienced clinician and three hours of practice on subjects' normal knees. Thirty normal subjects were measured by two novice testers during separate occasions. Testing was performed to determine anterior displacement values on both knees of each subject at 67N, 89N, and 133N force loads. The novice testers mean anterior displacement measures were similar to those measures in the literature. Additionally. previous studies suggested that a greater than 2mm side-to-side knee displacement difference is diagnostically valuable to assess ACL damage. This study also examined if normative measures greater than 2mm occurred within this normal sample. The data revealed that many normal subjects (23%) exhibited a displacement difference of greater than 2mm and suggested that with novice users, the device indicated many false positive readings. Lastly, the authors analyzed the intertester reliability of this device and found that statistically, this reliability was fair for anterior displacement data for 89N force (r= .780). Although statistically significant, clinical intertester reliability of side-to-side differences was found to be poor for novice testers (r=.700, 89N). The data obtained in this study also revealed that force load does not markedly affect variability in anterior displacement measures.


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