Hawaii Massage License Practice Exam

Which muscle is primarily involved in extension of the knee?

1. Biceps femoris

2. Rectus femoris

3. Sartorius

4. Semitendinosus

The correct answer is: Rectus femoris

The rectus femoris, part of the quadriceps muscle group, plays a key role in extending the knee. As a biarticular muscle, it crosses both the hip and knee joints, allowing it to contribute to knee extension as well as hip flexion. During activities such as standing up, walking, or running, the rectus femoris is activated to straighten the leg at the knee. In contrast, other muscles listed have different primary functions. The biceps femoris and semitendinosus are primarily involved in knee flexion rather than extension, while the sartorius has functions that include hip flexion and knee flexion but is not the principal muscle for extending the knee. Understanding the actions of each muscle can provide clarity on their roles in movement and rehabilitation.