It really depends on what you mean by “bad knees.” Knee pain and discomfort can be caused by osteoarthritis, rheumatoid arthritis, traumatic injury, a history of knee surgeries, patellofemoral pain syndrome, and much more. So the first thing to do is undergo a medical evaluation to determine what specifically is causing your knee trouble. Your health care provider may recommend medical treatment, which could physical therapy. A registered physical therapist can give you specific treatments and exercises to relieve pain, restore function and strengthen the muscles supporting your knees while minimizing the risk of further damage.
Generally, low-impact and no-impact cardiovascular exercises — like swimming, water fitness classes, bicycling, recumbent stair climbing, and walking — are easier on the joints and recommended for people with joint problems.
Working with your health care team and a certified fitness professional is your best bet for developing a sustainable exercise program tailored to your specific needs. Finding safe and effective ways to stay as physically active as possible will help you reach your health and well-being goals — and help you feel your best each day.