The infection usually reaches the joints though the bloodstream, although some joints may become infected due to an injection, surgery, or injury. Different bacteria and viruses can infect a joint and usually are associated with a person s age.
Joints are the areas where two bones meet.
Most joints are mobile, allowing the bones to move. Cartilage helps reduce the friction of movement. There are many different types of joints and they are classified according to structure and to how they move. Joints that do not move are called fixed. Other joints may move a little, such as the vertebrae.