What is the primary action of the L3 myotome?

The primary action of the L3 myotome pertains to knee extension. The L3 nerve root is responsible for innervating the quadriceps muscle group, which plays a crucial role in extending the knee joint. This action is vital for various functional activities, including walking, running, and climbing stairs, as it allows for stability and propulsion during movement.

While the other options involve actions associated with other myotomes or muscle groups, they do not align with the primary function of the L3 nerve root. Ankle dorsiflexion is primarily controlled by the L4 and L5 myotomes; knee flexion is predominantly the function of the hamstring muscles, which are influenced more by L5, S1, and S2; and hip extension is mainly governed by L5 and S1, affecting the gluteus maximus and hamstrings. Therefore, knee extension is the distinct action linked to the L3 myotome, making it the correct choice in this context.