Knee Valgus vs. Knee Abduction Angle: Comparative Analysis of Valgus Alignment Measurement Methods in Female Athletes

Abstract

Precise mathematical methods have been developed to quantify lower limb kinematics in anatomically meaningful ways to aid clinicians and researchers in a range of ways from injury prevention to rehabilitation practices. The improvement of technology in recent years, namely motion capture and non-invasive imaging, has resulted in an increase in research utilizing angles associated with human anatomy. Now, measuring lower extremity joint angles is a standard practice in many labs and clinics. Knee valgus angle (KVA), the angle created when the shank is rotated away from the midline of the body, has shown to correlate with subsequent anterior cruciate ligament (ACL) ruptures when measured during drop-jump tasks. As a result, this angle has garnered much attention in the field of biomechanics. KVA can be calculated in multiple ways by modifying the defined frontal plane and reference axis. The extensive research with KVA and the varying methods used to calculate the angle has led to ambiguity on how these different KVAs relate to one another and on the importance of individual joint angles that comprise KVAs. Additionally, changes in processing methods, namely the modification of the lower extremity joint constraints, and changing the movement task in which KVA is measured can influence the value of KVA. To study this angle, the kinematics of 23 female athletes, D1 soccer, D1 basketball, and club soccer (height = 171.2 +/- 88.9cm$, weight = 66.3 +/- 8.6kg, age = 19.8 +/- 1.9yrs), was analyzed using a motion capture system during tasks related to their sport and daily living. This work aims to determine the relationship between KVA calculated with different mathematical methods, kinematic processing models, and different movement tasks as well as to determine how the combination of lower extremity joint angles contribute to multiple types of KVA so that researchers and clinicians can properly evaluate KVA.