Causes
As you move or put pressure on a joint, cartilage allows bones to slide over one another and acts as a shock absorber. Cartilage itself does not have any nerve cells and therefore cannot sense pain. OA results when the cartilage becomes worn out, allowing the bones underneath to rub against each other causing pain and swelling. As the condition progresses, the joint may become disfigured and small growths called osteophytes begin to grow inside the joints. Osteophytes are small, irregular, bony growths that are also called bone spurs. Bits of broken-off cartilage or bone are also found floating inside the joint. This causes even more pain, swelling and immobility of the joint.
The exact cause of these changes is unknown. Scientists believe that the following factors play a role:
- increasing age: The cartilage wears down with time
- family genes: Scientists believe that osteoarthritis may be passed on through families with the symptoms appearing in middle age.
- being overweight: Excess weight puts stress on the weight-bearing joints such as hips and knees, and increases the risk of cartilage breakdown
- injury: Trauma to the joint, such as overuse, can damage the cartilage and lead to osteoarthritis. This is often the cause of OA in younger people.
- other types of arthritis such as rheumatoid arthritis can also damage joints and lead to osteoarthritis.