Muscles that act on the knee joint exhibit which two actions?

Muscles that act on the knee joint are primarily responsible for flexion and extension, which are the main movements that occur at this joint. Flexion refers to the bending of the knee, which primarily involves the hamstring muscles and the gastrocnemius, bringing the heel toward the buttocks. Extension, on the other hand, is the straightening of the knee, primarily carried out by the quadriceps muscle group, which extends the leg out in front of the body.

Understanding these actions is essential for grasping the functional biomechanics of the knee joint during various activities such as walking, running, or jumping. While other muscle actions like rotation and stabilization may occur to a lesser extent in specific contexts (such as during certain sports or injuries), the primary and most significant movements associated with the knee joint remain flexion and extension. This distinction is crucial for recognizing how the knee joint contributes to overall lower limb motion.