Which of the following joints is an example of a hinge joint?

• A. Shoulder joint
• B. Knee joint
• C. Wrist joint
• D. Hip joint

Answer: (B)

Hinge joints move mainly in one plane around a single axis, producing flexion and extension much like a door hinge. The knee fits this pattern, as people primarily bend and straighten it during activities and massage work. The shoulder is a ball-and-socket joint, which allows movement in many directions and rotation, not just one plane. The wrist is a condyloid (ellipsoidal) joint, which permits flexion, extension and some side-to-side movement but not pure hinge motion. The hip is another ball-and-socket joint with a wide range of movements in multiple planes. So the knee is the example that best fits a hinge joint.