Can joints wear out?
Joints can become diseased or wear out after a lifetime of use. When this happens, the cartilage or the fluid inside the joint gradually disappears. The joint becomes hard to move and may be very painful.
How many joints do I have?
The human body has more than 100 joints. Some joints move like a simple hinge, such as those in the elbows and knees. Other joints move in all directions, such as the shoulder joint or the base of the thumb. Joints in the spine allow only a small amount of movement between the vertebrae that protect the spinal cord. Joints such as the bones of the skull and those joining the two sides of the pelvis are locked firmly together so they do not move at all.
Pictures Credit: Google