Swelling is not usually present, but when found is due to normal, activity-related trauma to the joints. Swelling can cause an increase in fluid within the joint cavity. Signs of inflammation, such as joint redness and heat, are usually absent. Fluid may come and go within hours. The anatomy of a joint The area where two bones meet is called a joint.
All joints have a cavity containing a small amount of synovial fluid that allows for movement.
The attached tendons, muscles, ligaments and joint capsule hold the joint in its correct position. Looseness of these supporting structures allows a joint to have extra motion. Often, even normal activities that put stress on loose joints will irritate them. To illustrate how a joint works, think of a door hinge and a doorstop. The hinge is like a joint, and the doorstop prevents the door from swinging too far and damaging the wall.