PHILADELPHIA (CBS) - Osteoarthritis is a condition that affects many people as they get older. It often happens in the knee. Here is what happens in osteoarthritis.

The protective cartilage in the joints wears down over time. It is more common in people over fifty and people who are overweight. The cartilage acts like a cushioning surface in the body and when it is damaged a person can actually have areas of a joint where bone rubs against bone.

The most common symptom is – not surprisingly – pain. In addition, with activity, there is a limited range of motion, stiffness, tenderness and swelling around the knee. Often people will say they feel as if their knee is going to give out.

Pain medicine can help as well as physical therapy . Exercise and weight loss can make a big difference as can sports which are less traumatic.

Reported By Dr. Brian McDonough, KYW Newsradio Medical Editor