A reduction in the normal amount of this cartilage tissue causes some forms of arthritis. Normal wear and tear cause OA, one of the most common forms of arthritis. An infection or injury to the joints can exacerbate this natural breakdown of cartilage tissue.
Not everyone develops osteoarthritis. It is not an inevitable condition. Risk factors increase the likelihood you will develop osteoarthritis, but people can develop the disease who have none of the known risk factors.
Osteoarthritis. Osteoarthritis the most common form of arthritis.
Rheumatoid Arthritis. Rheumatoid arthritis is an autoimmune disease, which means that the 
the immune system attacks parts of the body—especially the joints.

1. How to avoid achy joints. You can't always prevent arthritis.
2. Eat fish. Certain fish are rich in omega-3 fatty acids, a healthy polyunsaturated fat. 
3. Control your weight. Your knees have to support your body weight. 
4. Exercise.
5. Avoid injury.
6. Protect your joints.
7. See your doctor.