Knee joint and elbow joints are examles of

Options

A. Saddle joint
B. ball and socket joint
C. pivot joint
D. hinge joint

Answer

### Step-by-Step Solution:

1. **Identify the Joints**: The question asks about the knee joint and elbow joint. We need to determine what type of joint they are.

2. **Understand Joint Functionality**: Both the knee joint and elbow joint allow for angular movement. This means that they can bend and straighten, which is a key characteristic we need to consider.

3. **Movement in One Plane**: The angular movement in these joints primarily occurs in one plane. This is an important feature that helps in classifying the type of joint.

4. **Angle Adjustment**: In both the knee and elbow joints, the angle between the two bones can either increase (extension) or decrease (flexion). This further supports our classification.

5. **Identify Joint Type**: Given the characteristics of angular movement in one plane and the ability to change the angle, we can classify both the knee and elbow joints as hinge joints.

6. **Terminology**: Hinge joints are also known as diarthrosis, which means they are freely movable joints. This classification confirms our identification.

7. **Final Answer**: Therefore, the knee joint and elbow joint are examples of hinge joints.