Did you know that when people say that they are double jointed they do not actually have an extra joint? They just have ligaments that can stretch beyond normal range.
Joints, Types of Bones, What Makes up a Bone
Ball and socket joints
Ball and socket joints:
Make a fist with one of your hands, then take your other hand and cup it around the other fist. That is basically the concept of a ball and socket joint. A ball and socket joint allows the part that fits in to the joint to move freely. For example the upper arm fits into the shoulder blade, and the upper leg fits into the hip. You could swing either of those in a full circle.
A hinge joint works like a door. A hinge joint only moves back and forth. Your knuckles, knees, and elbows all are hinge joints. In fact your knee is the biggest joint in the body.
With a saddle joint you do not have as much freedom as a ball and socket joint. The saddle joint allows your thumb to help pick up tiny objects such as needles or threads. There are saddle joints ankles and the wrists. The saddle joints in the ankle allow you to lean forward or backward, or stand on your tip toes.
The pivot joint is located at the top of the spinal column. The pivot joint allows your head to move side to side.
When a baby is born there are gaps called fontanels in an infant's cranial bones. Instead of bone there is a white membrane protecting the brain. By the time the baby is 15 months through 2 years of age there are fibrous, zigzagging joints called sutures will have sealed the gaps in their skull. Suture joints are impossible to move.
In between each vertabrae there are gliding joints. They allow very little movement as the two flat surfaces glide over each other. The gliding joints allow us to twist and bend all over the place.