The knee valgus angle (KVA) is heavily researched as it has been shown to correlate to ACL injuries when measured during jumping activities. Many different methods of KVA calculation are often treated as equivalent. The purpose of this study is to elucidate differences between these commonly used angles within and across activities to determine if they can indeed properly be treated as equivalent.
The kinematics of 23 female athletes, D1 soccer, D1 basketball, and club soccer (height = 171.2 ± 8 8.9cm, weight = 66.3 ± 8.6kg, age = 19.8 ± 1.9yrs), was analyzed using a motion capture system during activities related to their sport and daily living.
The abduction KVA, measured using body fixed axes, only correlated to the two-dimensional global reference frame angle (KVA 2G) in three of the six activities (walking, squatting, and walking down stairs), and one out of six in the 3D measurements (jogging). This suggests that the abduction KVA does not always relate to other versions of KVA.
The KVA with reference to the pelvis coordinate system (KVA 2P) correlated to the KVA 2G in six out of six activities (r= 0.734±0.037, P=<<0.001) suggesting the pelvis can be utilized as a reference plane during rotating tasks when a fixed global system is less meaningful. Not all measures of KVA are equivalent and should be considered individually for this population. Thoroughly understanding of the equivalence of various measures of KVA is essential in understanding ACL injury risk.