Question

Which of the following is an example of hinge joint?

• A. Between the carpals
• B. Between carpal and metacarpal of thumb
• C. Knee joint
• D. Between atlas and axis

Hint:

To easily identify hinge joints, think of structures that primarily allow bending and straightening in a single plane. Common examples include the elbow, knee, ankle, and the interphalangeal joints of the fingers and toes.

Answer 1

The Correct Option is C

What is a Hinge Joint?

A hinge joint is a type of synovial joint that allows movement in one plane, much like the hinge of a door. These joints allow flexion and extension, enabling the body part to bend and straighten. Hinge joints are uniaxial, meaning they only allow movement along one axis.

Understanding the Options

Let’s examine each option to determine which one is an example of a hinge joint:

1. Between the Carpals

The carpals are the bones in the wrist. The joint between them is a gliding joint, not a hinge joint. Gliding joints allow limited movement, primarily sliding or gliding over each other, but they do not allow the bending and straightening characteristic of hinge joints. So, this option is incorrect for a hinge joint.

2. Between Carpal and Metacarpal of Thumb

The joint between the carpal and metacarpal of the thumb is a saddle joint, not a hinge joint. A saddle joint allows movement in two planes, providing a greater range of motion than a hinge joint. It is found at the base of the thumb, enabling actions like grasping and opposable thumb movements. Thus, this option is incorrect for a hinge joint.

3. Knee Joint

The knee joint is a classic example of a hinge joint. It allows movement primarily in one plane: flexion (bending) and extension (straightening). The knee joint allows the lower leg to move forward and backward, much like the movement of a door on a hinge. This makes the knee joint the correct example of a hinge joint.

4. Between Atlas and Axis

The joint between the atlas and axis (the first two cervical vertebrae) is a pivot joint, not a hinge joint. This joint allows the head to rotate from side to side, like shaking the head "no." Pivot joints allow rotational movement, which is different from the back-and-forth movement of hinge joints. So, this option is incorrect for a hinge joint.

Why Knee Joint is the Correct Answer

The knee joint is the most straightforward example of a hinge joint in the body. It allows movement along one axis—flexion and extension—making it a classic example of a hinge joint.

Why Not the Other Options?

• Between the Carpals: This is a gliding joint, not a hinge joint.
• Between Carpal and Metacarpal of Thumb: This is a saddle joint, which allows movement in multiple planes.
• Between Atlas and Axis: This is a pivot joint, allowing rotational movement.

A Simple Way to Remember

Here’s a simple analogy:

• Hinge Joint: Like the hinge of a door, the knee joint allows bending and straightening.
• Saddle Joint: Like a saddle, it allows movement in multiple directions, as seen in the thumb.
• Pivot Joint: Like a doorknob rotating, the joint between atlas and axis allows rotational movement of the head.

Final Answer

The correct answer is Knee joint, as it is a perfect example of a hinge joint that allows movement in one plane—flexion and extension.