A novel measure of in-vivo knee joint laxity

Current measures of knee joint laxity, such as those found clinically using the KT-2000 arthrometer, are not highly repeatable or reliable (Huber et al, 1997). In this study, a non-invasive in-vivo Magnetic Resonance imaging-based measure of laxity, the Knee Loading Apparatus (KLA), was designed and evaluated with five normal subjects (repeatability study, n=3). Effects of total body water content, hormones, and muscle guarding were considered. When compared to the KT-2000, the KLA was found to be less variable (±0.58 mm vs. ±1.47 mm). Future KLA design iterations should aim to control the initial positioning of the subject, a finding that may shed light on the low reliability of the KT-2000. The KLA enabled quantification of both in-vivo knee joint stress relaxation and ACL (ligament specific) laxity for the first time. The KLA shows promise as an accurate and reliable tool for measuring in-vivo joint and ligament laxity, and viscoelastic behavior.