Real-time ultrasonographic characteristics of the lateral collateral ligament of the knee in cross-leg position with varus stress maneuver

Background: Acute injury to the lateral collateral ligament (LCL) of the knee joint usually occurs in conjunction with anterior (ACL) or posterior (PCL) cruciate ligament tears. Failure to notice an LCL injury can cause failure in ACL or PCL reconstruction surgeries. Some authors have proposed the use of ultrasonography (US) to diagnose LCL injury. However, the poor sonographic imaging quality of the LCL produces a hypoechoic and compact configuration. The aim of this study was to compare the ultrasound imaging quality of the LCL from two different postures: a cross-leg position with the knee varus stress maneuver and the knee extension position. Methods: This was a cross-sectional study with 64 healthy subjects. A US examination with a 5-12MHz linear transducer was used to evaluate the LCL. Each subject was first assigned randomly to either the cross-leg position or the knee extension position, and, 10 minutes later, changed to the other position. Ultrasonographic measurements obtained included the widths and grey-scale histograms of the LCL when the subjects lay in the cross-leg position with the knee varus stress maneuver and knee extension position. The angle between the LCL and the horizontal line parallel to the US probe was also measured. Results: Our cross-sectional ultrasonographic study contained 64 subjects (22men, 42 women; age, 24.3 4.0y; height, 166.9 8.6cm; weight, 58.8 10.6kg) studied from July 2008 to October 2008. The mean thickness, grey-scale histogram of the LCL, and angle in the crossleg position with the knee varus stress maneuver differed significantly from those in the knee extension position. (all p < 0.05). Ultrasonographic study of the LCL in the cross-leg position with the knee varus stress maneuver permits improved ultrasonographic visualization of the LCL. Conclusions: The cross-leg position with the knee varus stress maneuver is a more effective way of stretching the LCL than using the knee extension position. US is "operator-dependent" as well as "position-dependent". Our study revealed better US image quality of the LCL in the cross-leg position with the knee varus stress maneuver.