In a normal joint (where two bones come together), the muscle, bursa and tendon support the bone and aid movement. The synovial membrane (an inner lining) releases a slippery fluid into the joint space. Cartilage covers the bone ends, absorbing shocks and keeping the bones from rubbing together when the joint moves.
A person with an arthritic joint, has a problem with one or more of these pliable structures. These structures get damaged or degenerate over the years (by movement or other factors), and cause symptoms like pain, stiffness, swelling and joint fever. These symptoms can occur atdifferent intervals and intensities, depending on the individual or the extent of the damage.

