Ball-and-socket joint facts for kids

Quick facts for kids Ball and socket joint
1: Ball and socket joint; 2: Condyloid joint (Ellipsoid); 3: Saddle joint; 4 Hinge joint; 5: Pivot joint;
Capsule of shoulder-joint (distended). Anterior aspect.

The ball-and-socket joint (also known as a spheroid joint) is a special type of joint found in your body. Imagine a round ball fitting into a cup! One bone has a rounded, ball-shaped end, and it fits perfectly into a cup-shaped hollow in another bone. This amazing design allows the joint to move in almost every direction, like swinging your arm around in a circle.

These joints are a type of synovial joint. This means they have a space filled with fluid that helps the bones move smoothly without rubbing. The "ball" bone can spin and move around many different imaginary lines (axes) that all meet in the middle of the joint. This is why you can move your arm or leg in so many ways!

Where are ball-and-socket joints found?

You have these super flexible joints in a few key places in your body. They are essential for many everyday movements, from walking to throwing a ball.

The Hip Joint

Your hip is a great example of a ball-and-socket joint.

• The round top part of your femur (your thigh bone) is the "ball."
• This "ball" fits into a cup-shaped hollow called the acetabulum. The acetabulum is part of your pelvis (your hip bone).

This joint helps you walk, run, and kick. It's very strong and stable.

The Shoulder Joint

Your shoulder joint is another important ball-and-socket joint.

• The rounded top part of your humerus (your upper arm bone) is the "ball."
• This "ball" fits into a shallow, cup-like area called the glenoid cavity. This cavity is part of your scapula (your shoulder blade).

The shoulder joint is the most flexible joint in your body. It lets you raise your arm, throw, and reach in almost any direction.

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  The hip joint, showing the ball-and-socket structure.

• 

  The shoulder joint, which is also a ball-and-socket joint.

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  Detailed view of the hip joint.

• * Femur
• * Femoral Neck
• * Femoral Head
• * Acetabulum
• * Acetabular Labrum
• * Pelvis

See also

In Spanish: Enartrosis para niños