What is the primary action of the sartorius muscle?

The primary action of the sartorius muscle includes flexing the hip, extending the stifle (knee), and also flexing the stifle. This muscle runs from the ilium (part of the pelvis) down to the tibia and plays a crucial role in both the hip and knee movements.

In detail, the sartorius assists in flexing the hip as it draws the thigh forward. It also aids in flexing the stifle, which is essential for movements such as walking or running. The dual action of extending the stifle is notable because the sartorius not only helps in bending the knee but can also stabilize the joint in certain positions.

This multifaceted role makes the sartorius an important muscle in activities that involve both hip and knee movements, which is why B accurately describes its primary function.