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Contributor: Hannah Brooks. Lesson ID: 12637
Some animals, like birds and camels, seem to have backward knees! In truth, what we think are their knees are really their ankles! Confusing? Learn about how our human joints work; it's more amazing!
Hinges help us move through our environment easily, opening and closing doors with little effort.
Sometimes, those hinges do not work as well as they should and can even produce a creaking noise like the one in the video below.
How well your body moves hinges on the hinges in your body, that work just like the hinges on a door! Only yours don't get rusty!
The human body has hinges called joints!
Joints exist anywhere that two bones meet. Examples of important joints include knees, elbows, and wrists.
Joints allow the skeletal and muscular systems to work together for human movement and growth. Read on to learn more about the types of joints in the human body!
Immovable joints do not move but do contain connective tissues that link the edges of bones. You have immovable joints in your skull and jaw. These are the joints that hold your teeth in the jaw!
Some joints move a little and are called partially moveable, or cartilaginous, joints.
These joints attach bones with cartilage. Cartilage is a tough, flexible connective tissue. It is found in joints and the top of your ear!
An example of a partially moveable joint is the spine. Each vertebrate in the spine is connected by cartilage, which allows some movement about other vertebrae. This structure prevents the spine from moving too freely, protecting it from injury.
Some joints move freely, like our ankles. These joints are called freely movable or synovial joints. They can move in various directions, depending on the location of the body.
Freely moveable joints are called synovial joints because these joints contain synovial fluid that acts as a lubricant for bone movement.
There are three types of synovial joints.
Hinge joints move in one direction. Think about how your knee or fingers move, only back and forth. These are hinge joints.
Pivot joints rotate or twist. Do a quick neck circle to demonstrate how your neck moves in a rotating motion.
Ball and socket joints allow for free movement in many directions. Your hips and shoulders are examples of ball and socket joints.
These types of joints both promote and restrict movement. They allow free movement in different directions based on the structure of the joint.
Bones and muscles determine the structure of joints. Bones provide the support, while muscles provide the flexibility — joints would not work without either component!
Move to the Got It? section to learn more about the types of joints!
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