The best low impact cardio for bad knees

For most ongoing knee pain, the kind that nags rather than the kind from a fresh injury, complete rest tends to make things worse over months. The muscles that stabilise the knee weaken, the joint stiffens, and you lose the fitness that keeps your whole body healthy. This is why major clinical guidelines for knee osteoarthritis, the most common cause of chronic knee pain, list structured exercise as a core treatment, right alongside education and weight management. Movement is the medicine, not the thing to avoid.

The goal is simply to change the type of movement. You want cardio that keeps your heart, lungs, and legs working without the repeated impact that angers a sore knee. The good news is that low impact does not mean easy. You can get thoroughly out of breath on a bike or in a pool. You are just trading pounding for gliding.

Here is the honest ranking, from the most joint-sparing to the borderline. Where you start depends on how your knee feels right now. You can always move up the list as it gets stronger.

If your knees are really unhappy, start in the water. Buoyancy supports a large share of your body weight, so your joints barely bear any load while your muscles and heart work fully. Swimming, water walking, and aqua-aerobics all let you push your cardiovascular system hard with almost no joint stress. Aquatic exercise is specifically recommended in osteoarthritis guidelines as a good option, particularly when land-based movement is still too painful.

It is also a confidence builder. Many people who have been avoiding movement because everything hurts rediscover in the pool that they can work hard without pain, which makes it easier to progress to weight-bearing options later. Think of water as the on-ramp.

For most people with bad knees, cycling is the best day-in, day-out choice. Your feet stay on the pedals, so there is no impact, and the smooth circular motion moves the knee through a controlled range that actually helps keep it mobile and nourished. A stationary bike is the safest version because you control the resistance and there is no risk of a fall.

• Set the seat height right. Too low forces a deep knee bend that can hurt. Your leg should be almost straight at the bottom of the pedal stroke, with just a slight bend.
• Start with light resistance. Spin at an easy pace and build up. Heavy resistance early on can strain the joint before the surrounding muscles are ready.
• Try a recumbent bike if pain is high. The reclined seat takes pressure off the knee and back, and it is easier to get on and off.
• Stop if you feel sharp pain. A dull working ache in the muscles is fine. Sharp or joint-line pain means adjust the setup or ease off.

Once your knee tolerates some weight-bearing work, the elliptical and incline walking are excellent. Both keep you upright and load the leg the way real life does, which builds useful strength, but without the repeated impact of running.

The elliptical guides your feet through a smooth oval so they never leave the pedals. It feels like a cross between walking and running but removes the landing, so it is a low-impact way to get your heart rate up while staying on your feet. Incline walking is even simpler: walking up a gentle grade lets you work hard at a slow, controlled pace, which is easier on the knees than fast flat walking or running because you are moving slowly. Keep the incline moderate and the pace comfortable, and back off if the downhill portion bothers you, since descending loads the knee more than climbing.

Cardio keeps you fit and mobile, but if you want your knees to genuinely feel better over time, the highest-value thing you can add is strength work for the muscles that support the joint. Strong quadriceps, hamstrings, and hip muscles act like shock absorbers and stabilisers, sharing the load that would otherwise fall on the joint surface.

You do not need to load heavy or do anything fancy. Bodyweight or lightly loaded movements like sit-to-stands from a chair, gentle step-ups, and controlled leg raises build the quads and glutes without stressing the joint. Guidelines put land-based strengthening exercise at the core of managing knee osteoarthritis for exactly this reason: it consistently reduces pain and improves function. Pair your low-impact cardio with two short strength sessions a week and you are doing the two things that help knees most.