A new device to measure knee laxity during weightbearing and non‐weightbearing conditions

The Vermont knee laxity device (VKLD) was developed to evaluate anterior—posterior (A—P) displacement of the tibia relative to the femur (A—P laxity) during weightbearing and non‐weightbearing conditions. The purposes of this study were to determine the repeatability and reliability of the VKLD measurements of A—P laxity and to compare them with two devices currently in clinical use: the KT‐1000 knee arthrometer and planar stress radiography. Two independent examiners tested six subjects with no history of knee injury. A—P laxity was measured on three separate days with the KT‐1000 and the VKLD. With the VKLD, A—P laxity was measured in the weightbearing and non‐weightbearing conditions. In addition, one examiner measured A—P laxity in each subject on each day using a planar stress radiography technique. Similar A—P laxity values were obtained with the KT‐1000 and the VKLD; however, the planar stress radiography technique measured less A—P laxity compared to the VKLD (9.2 ± 2.2 mm versus 13.3 ± 2.9 mm, P = 0.0004). None of the three devices showed significant differences in measuring A—P laxity between days. During weightbearing, A—P laxity was reduced by 65–70% compared to the non‐weightbearing condition (P = 0.0001). Future investigations will use the VKLD to study subjects that have suffered injury to the anterior and posterior cruciate ligaments. © 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.