Bones and joints are integral parts of the human body. The question of how many joints there are in the human body is a difficult one to answer because it depends on several variables. They are:
- Definition: Some define a joint as a point where 2 bones connect. Others suggest it is a point where bones connect to move body parts.
- Sesamoids: Sesamoids are bones embedded in tendons, but not connected to other bones. The patella is the largest sesamoid. These bones change in number from person to person.
- Age: Babies start with about 270 bones. Some of these bones fuse during growth. Adults have 206 named bones- 80 in the axial skeleton and 126 in the appendicular skeleton.
In short, there’s no definite answer to this question. The estimated number is between 250 and 350.
Types of freely movable joints
There are six types of freely movable joints. They are:
- Ball and socket joint: The ball and socket joint features the rounded head of one bone sitting in the cup of another bone and thereby permitting movement in all directions. Example- shoulder joint and hip joint.
- Hinge joint: The hinge joint is like a door, opening and closing in one direction, along one plane. Example- knee joint and elbow joint.
- Condyloid joint: The condyloid joint allows movement, but no rotation. Example- jaw joint and finger joint.
- Pivot joint: The pivot joint is also known as the rotary joint or trochoid joint. It is characterized by one bone that can swivel in a ring formed from a second bone. Example- ulna joint.
- Gliding joint: The gliding joint is also known as a plane joint. Although it only allows limited movement, it is characterized by smooth surfaces that can slide over one another. Example- wrist joint.
Saddle joint: Even though the saddle joint does not allow rotation, it enables movement back and forth as well as side to side. Example- thumb joint.