The Best and Worst Aerobic Exercises for Bad Knees

Next to bad backs, bad knees are the most often complained about injury, and they are usually cited as a reason not to exercise. But, in many cases, you can do cardio for bad knees.

The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) recommends a wide range of motion, strength and aerobic exercises to treat your bad knees. Having said this, not all exercises are created equal, and, to avoid injury, they should be done with proper form.

The tibia, or shin bone, fibula in the outer lower leg, femur in the thigh and patella (kneecap) — supported by muscles, tendons and ligaments — all make up the knee. When you have "bad knees," your range of motion is compromised. Your knees feel weak and might be unable to carry your weight or the demands of certain exercises, and they hurt.

More often than not, the reason your knees hurt is because the surrounding muscles such as your quads, hamstrings and calf muscles that support your knees are weak. Appropriate exercises to strengthen these muscles help reduce knee pain and sometimes eliminate it altogether.

When the culprit is not an overuse injury or weak supporting muscles, the cause of sore knees could also be osteoarthritis, a degenerative inflammatory condition affecting the bones and joint, according to Mayo Clinic.

Read more: The Best Workout for Bad Knees

High-impact exercises that place the most stress on the joints should be among the exercises not to do with bad knees. These include running, jogging and high-impact aerobics. Running is not usually the cause of knee pain — except in cases where there is obesity, previous injury or a predisposed risk of joint arthropathies, or joint disorders.

Going against the grain, a modest study published in a December 2016 issue of the European Journal of Applied Physiology confirmed that running for 30 minutes a day actually helped decrease inflammation in the joints of runners' knees. This is all to say that everything can be good in moderation. Check with your doctor to see what exercises are really best for your situation.

The knee is designed to bear weight and absorb shock, but it can be easily injured by incorrect movements and poor form during exercise. If your knees are sore, it's best to stop all weight-bearing exercises completely to avoid further damage. Opt for gentler forms of cardio until the knee is rehabilitated. Other aerobic exercises to be avoided are skipping, trampoline exercises, kick boxing and high-impact aerobic exercises.

The main culprits for knee injuries are skiing and trampoline bouncing, as the quick changes in direction and form, combined with impact, can cause injury.

Read more: Bad Knees? Try These 14 Knee-Strengthening Exercises

When creating your fitness routine, stick with low knee impact cardio like rowing, swimming and the elliptical — and you can still do a high-intensity workout for bad knees. These help keep the muscles strong without the added stress of high-impact exercises.

Cycling and water aerobics are also preferable options. However, the importance of consulting a doctor before you begin a new exercise program — especially if you've had previous injuries — is crucial and should not be avoided.