American Board of Surgical Assistants (ABSA) Orthopedic Practice Test

Which of the following joints operates mainly through flexion and extension?

1. Shoulder joint

2. Knee joint

3. Ankle joint

4. Wrist joint

The correct answer is: Knee joint

The knee joint is primarily designed to facilitate movements of flexion and extension. This hinge joint allows the leg to bend (flexion) at the knee to create an angle between the thigh and the lower leg, and to straighten (extension) to return to a straight position. This action is essential for various activities such as walking, running, and jumping, where the bending and straightening of the knee are crucial for mobility. In contrast, while other joints like the shoulder, ankle, and wrist also engage in flexion and extension, they are not limited to just these movements and allow for a wider range of motions. The shoulder joint, for instance, is a ball-and-socket joint capable of movements in multiple directions, including rotation. The ankle joint enables dorsiflexion and plantarflexion but also supports some degree of side-to-side movement. The wrist joint allows for flexion and extension, as well as radial and ulnar deviation, contributing to a more complex range of motion.