Ideally, everyone should get three types of exercise regularly:
- Range-of-motion exercises to help maintain normal joint.
- Strengthening exercises to help keep or increase muscle strength.
- Keeping muscles strong with exercises, such as walking up stairs, doing leg lifts or dips, or riding a stationary bicycle, helps support and protect the knee.
- Aerobic or endurance exercises to improve function of the heart and circulation and to help control weight.
- Weight control can be important to people who have arthritis because extra weight puts pressure on many joints. Some studies show that aerobic exercise can reduce inflammation in some joints.
If you already have knee problems, your doctor, chiropractor or health therapists can help with a plan of exercise that will help the knee(s) without increasing the risk of injury or further damage. As a general rule, you should choose gentle exercises such as swimming, aquatic exercise, or walking rather than jarring exercises such as jogging or high-impact aerobics.
http://www.niams.nih.gov/Health_Info/Knee_Problems/default.asp#19
