What Exercise Is Best for Knee Arthritis? A New Study Has Answers

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Introduction

If you’re one of the millions of people living with knee osteoarthritis, you’ve probably heard the same advice from doctors, physical therapists, and well-meaning friends: “You should exercise.” But if your knees hurt when you walk, climb stairs, or even just stand up from a chair, the thought of exercising might feel overwhelming—or even impossible.

Here’s the good news: a massive new study published in the British Medical Journal (BMJ) has analyzed 217 clinical trials involving more than 15,600 people to answer a question that has puzzled both patients and doctors for years: Which type of exercise actually works best for knee arthritis?

The answer is clearer than ever before—and it might surprise you.

Why This Study Is Different (And Why You Can Trust It)

Before we dive into the results, let’s talk about why this study matters. Medical research can be confusing, especially when one study seems to say one thing and another says something completely different. What makes this particular study stand out?

First, the researchers didn’t just look at a handful of studies. They systematically searched through 45,804 potential research papers, carefully winnowing them down to the 217 highest-quality randomized controlled trials. That’s the gold standard in medical research—studies where people are randomly assigned to different treatments so researchers can truly compare results.

Second, they used the most up-to-date tools for evaluating study quality, including something called RoB 2 (Risk of Bias 2), which provides a more accurate assessment of whether a study’s findings are reliable. They also applied the GRADE framework, an internationally recognized system for rating the confidence we can have in medical evidence.

Third—and this is crucial—they looked at outcomes at different time points: short-term (about 4 weeks), medium-term (about 12 weeks), and long-term (about 24 weeks). Knee arthritis is a chronic condition that doesn’t go away, so understanding how exercise helps over time is essential.

Finally, the study was published in the BMJ, one of the world’s most respected medical journals, and underwent rigorous peer review. One of the peer reviewers was actually a patient with knee osteoarthritis, ensuring the findings would be meaningful to real people, not just researchers.

The Big Winner: Aerobic Exercise

So what did they find? Aerobic exercise emerged as the clear winner across multiple measures.

When we talk about aerobic exercise, we mean activities that get your heart pumping and your lungs working—walking, cycling, swimming, or using an elliptical machine. Not running marathons, but sustained, moderate activity that you can maintain for 20-30 minutes.

Here’s what the study found about aerobic exercise:

For pain relief: Aerobic exercise produced “large improvements” in pain at both short-term (4 weeks) and medium-term (12 weeks) follow-ups. The effect was so significant that researchers used words like “probably results in a large reduction in pain”—strong language for cautious scientists.

For physical function: At medium-term follow-up, aerobic exercise showed large improvements in how well people could move and perform daily activities. Even at long-term follow-up (24 weeks), the benefits continued.

For walking and movement: Gait performance—how well you walk—improved significantly with aerobic exercise at medium-term follow-up.

For quality of life: At short-term follow-up, aerobic exercise produced large improvements in how people rated their overall well-being.

When the researchers ranked all exercise types across all outcomes, aerobic exercise consistently ranked highest. Think of it as the straight-A student in this comparison.

Why Aerobic Exercise Eases Knee Pain: The Science Explained

You might wonder: if your knee pain comes from damaged cartilage and worn-out joints, how can something as simple as walking or swimming actually help? The answer lies in the remarkable ways your body responds to aerobic exercise—effects that go far beyond just “strengthening muscles.”

It Reduces Inflammation at the Cellular Level

One of the most powerful benefits of aerobic exercise is its ability to calm inflammation throughout your body, including in your knees. When you engage in moderate aerobic activity, your muscles release small proteins called myokines into your bloodstream. Think of myokines as nature’s anti-inflammatory medicine.

Interleukin-6 (IL-6) is one of the most important myokines released during exercise. Unlike the harmful inflammation that drives arthritis pain, exercise-induced IL-6 actually suppresses the production of TNF-alpha, a major inflammatory chemical involved in osteoarthritis. Regular aerobic exercise creates an environment where anti-inflammatory signals dominate, potentially slowing the progression of joint damage while reducing pain.

It “Washes” Your Joints with Nutrient-Rich Fluid

Your knee joints contain synovial fluid—a thick, egg-white-like substance that nourishes cartilage and acts as a shock absorber. But here’s the catch: cartilage has no direct blood supply. It depends entirely on movement to stay healthy.

When you walk, cycle, or swim, the compression and release of your knee joints creates a pumping action that circulates synovial fluid. Think of it as squeezing and releasing a sponge. This movement delivers oxygen and nutrients to cartilage cells while flushing out waste products. Without regular movement, cartilage slowly starves and deteriorates faster. Aerobic exercise keeps this natural “joint-washing” system working properly.

It Changes How Your Brain Perceives Pain

This is one of the most fascinating findings in recent pain research. Aerobic exercise triggers the release of endorphins—your body’s natural painkillers—but it does something even more profound. Regular aerobic activity actually reshapes how your central nervous system processes pain signals.

Through a process called “descending pain modulation,” aerobic exercise strengthens your brain’s ability to turn down the volume on pain signals coming from your knees. People with chronic pain often lose this natural pain-dampening ability. Aerobic exercise helps restore it. This is why people who exercise regularly often report that their knees feel better not just during activity, but throughout the day.

It Improves Biomechanics and Reduces Joint Load

Aerobic exercise, particularly walking and cycling, improves how you move. When knee arthritis alters your gait—perhaps you limp or shift weight awkwardly—you place uneven stress on already damaged joints. This creates a vicious cycle: pain changes how you walk, and walking differently increases pain.

Regular aerobic activity helps maintain a normal, symmetrical gait pattern. It also promotes better alignment of your hips, knees, and ankles during movement. Over time, this means the forces of walking are distributed more evenly across your joint surfaces rather than concentrated on damaged areas. Less stress on painful spots means less pain.

It Promotes Weight Management

While not the only factor, weight management plays an important role in knee arthritis. Every pound of body weight translates to roughly three to four pounds of force across your knee joints during walking. For someone who is 30 pounds overweight, that’s an extra 90-120 pounds of force hammering their knees with every step.

Aerobic exercise, combined with sensible eating, helps create the calorie deficit needed for weight loss. But even without significant weight loss, aerobic exercise improves how your body processes fat and sugar, reducing the harmful metabolic factors that can worsen arthritis inflammation.

It Builds the “Muscle Shield” Around Your Knee

While strengthening exercises directly build muscle, aerobic exercise—particularly walking on varied terrain, cycling, or using an elliptical—also activates and conditions the muscles surrounding your knee. Your quadriceps (front thigh muscles), hamstrings (back thigh muscles), and calf muscles work together as a dynamic support system for your knee joint.

Stronger muscles act like shock absorbers, taking some of the force that would otherwise hammer your cartilage and bone. This “muscle shield” effect explains why people with stronger legs typically experience less knee pain even when their X-rays look similar to those with weaker legs.

The Cumulative Effect: Why Consistency Matters More Than Intensity

Here’s what makes aerobic exercise particularly powerful for knee arthritis: the benefits compound over time. The anti-inflammatory effects build with regular activity. The cartilage-nourishing benefits accumulate with each walk. The pain-processing changes in your brain strengthen with repetition. This is why the BMJ study found benefits at 4 weeks, even stronger benefits at 12 weeks, and maintained improvements at 24 weeks.

The type of aerobic exercise matters less than doing it consistently. Walking is the most accessible option—free, requires no equipment, and can be done anywhere. Swimming and water aerobics offer the added benefit of buoyancy, reducing joint stress while providing resistance. Cycling, whether stationary or outdoor, provides excellent cardiovascular benefits with minimal joint impact

But Wait—What About Other Types of Exercise?

The study also looked at several other exercise modalities. Here’s what they found:

Strengthening exercise (like leg presses, squats, or using resistance bands) showed large improvements in function at medium-term follow-up. This makes intuitive sense—stronger muscles around the knee can better support the joint.

Mixed exercise—combining different types like strengthening plus flexibility or strengthening plus aerobic—also showed strong benefits for function at medium-term follow-up. Interestingly, 88% of mixed exercise programs included strengthening as a core component, suggesting that building muscle strength is a key ingredient.

Mind-body exercise (think tai chi, yoga, or Pilates) likely results in substantial improvements in function at short-term follow-up. These exercises may help with body awareness, balance, and the mental challenges of living with chronic pain.

Neuromotor exercise, which focuses on balance, coordination, and proprioception (your brain’s awareness of where your body is in space), showed large improvements in gait performance at short-term follow-up.

Flexibility exercise (stretching) may reduce pain at long-term follow-up, though the evidence was of lower certainty.

What About Safety?

If you’re worried that exercise might worsen your knees, the study offers reassurance. Only 40 of the 217 studies (18%) reported on adverse events, but among those that did, there was no clear evidence that any exercise type caused more problems than the control group. In plain language: exercise appears to be safe for people with knee osteoarthritis.

The confidence intervals were wide, meaning we can’t say with absolute certainty that one exercise is safer than another, but the overall picture suggests that the benefits of exercise far outweigh the risks.

A Closer Look at the Numbers

For those who appreciate details, let’s look at some specific findings. The researchers used something called “standardized mean difference” to measure effects, with 0.5 considered the threshold for a “minimal important difference”—the point at which patients actually notice a change.

For pain at 12 weeks, aerobic exercise showed an effect size of -1.19 (negative numbers indicate less pain). That’s more than twice the minimal important difference, meaning people aren’t just slightly better—they’re substantially better.

For function at 12 weeks, aerobic exercise showed an effect size of 1.78, again far exceeding the 0.5 threshold. Mixed exercise (1.07) and strengthening (0.86) also exceeded the threshold.

The researchers took a conservative approach, using the 0.5 threshold. But they note that if a lower threshold of 0.2 were used—which some researchers consider meaningful—even more exercises would show benefits, particularly at long-term follow-up.

What This Means for You

So how do you translate this research into your daily life? Here are practical takeaways:

If you can do only one type of exercise, make it aerobic. Walking is free, requires no equipment, and can be done almost anywhere. Start with what you can manage—maybe 10 minutes a day—and gradually work up. The key is consistency, not intensity.

But don’t abandon other exercises entirely. The study suggests that different exercises offer different benefits. Strengthening supports your joints, mind-body exercises help with body awareness, and flexibility work may help with long-term pain management. Think of aerobic exercise as your foundation, with other types as valuable additions.

Listen to your body, but don’t let fear stop you. The safety data is reassuring. Some discomfort during exercise is normal—your muscles are working—but sharp pain that makes you catch your breath is a signal to stop or modify.

Be patient. Knee arthritis didn’t develop overnight, and exercise benefits take time to accumulate. The study shows benefits at 4 weeks, as well as at 12 and 24 weeks, suggesting that sticking with it pays off.

Why Your Doctor Might Not Have Told You This

If aerobic exercise is so clearly beneficial, why haven’t you heard this before? Several reasons:

First, medical guidelines have traditionally recommended exercise in general terms without specifying which type is best. Doctors have been left to rely on expert opinion and clinical experience rather than clear evidence.

Second, this study is brand new—published in 2025—and it takes time for research to filter down to clinical practice. Your doctor may not have seen it yet.

Third, to date, no study has compared these exercise types across time points with such rigorous methodology. Previous research often lumped results from different follow-up periods together, potentially missing important patterns.

The Bottom Line

If you’re living with knee osteoarthritis, this study offers clear, practical guidance: Make aerobic exercise your priority. Whether it’s walking, swimming, cycling, or another activity you enjoy, consistent aerobic exercise likely offers the best combination of pain relief, improved function, better mobility, and enhanced quality of life.

But don’t throw out your resistance bands or give up on yoga. The best exercise program is probably one that combines aerobic activity with strengthening, balance work, and flexibility, with aerobic exercise as the star player.

As the researchers note, “Exercise treatment offers obvious benefits for individuals with knee osteoarthritis.” This study helps us understand exactly which benefits to expect and how to achieve them.

Start where you are. Use what you have. Do what you can. Your knees will thank you.

Don’t Get Sick!

About Dr. Jesse Santiano, MD

Dr. Santiano is a retired internist and emergency physician with extensive clinical experience in metabolic health, cardiovascular prevention, and lifestyle medicine. He reviews all medical content on this site to ensure accuracy, clarity, and safe application for readers. This article is for educational purposes and is not a substitute for personal medical care.

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References:

• This article is based on “Comparative efficacy and safety of exercise modalities in knee osteoarthritis: systematic review and network meta-analysis,” published in BMJ 2025;391:e085242. The study was conducted by an international team of researchers and included 217 randomized controlled trials with 15,684 participants. https://www.bmj.com/content/391/bmj-2025-085242

Disclaimer:
This article is for educational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician before making health decisions based on the TyG Index or other biomarkers.

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