That we have no joints in the body, we would not be able to move. We could only lay completely motionless, unable to move our head, to walk, to raise our hands or to move a finger! And we can do that thanks to the joints.
Everywhere where two bones glide over one another is joint. Joints allows bones to smoothly run with very little friction, because the ends of the bones are covered with cartilage, so that the bone does not grind against each other. In addition, in the joint is located a whitish, synovial fluid; it plays the role of lubricating oil of the machine, it reduces friction. When joint is at a standstill, creating very little synovial fluid and joint becomes really creaky.
In the human body there are four types of joints: angular, egg-shaped, in the form of hinge (wrists) and rotary joint. The shoulder joint, which is spherical – ball joint, is the most mobile of all joints in the body. Therefore, we can move hand in all directions. The hip joint is the largest ball joint, but because it is deeper, there is no so great mobility.
Did you know; the iliofemoral ligament is strongest ligament in the human body and as such is an important constraint to the hip joint.
The third type of joint is a joint in the form of a hinge. There the bones can only move forward and back in one plane, such as doors. The joints between the phalanges are joints in the form of a hinge.
The fourth type is the rotary joint. It allows bones to spin. Rotating joint we have in base of the skull, so that we can turn our heads and joint at the elbow allows us to turn the key in the lock.
Read also How do Artificial Hips Work!