Exercise for Knee Osteoarthritis: What the Research Says

If your knees ache going down stairs, stiffen up after you sit too long, or grumble on the first few steps out of bed, you have probably been told two contradictory things. Rest it. And use it. That confusion is one reason knee osteoarthritis feels so frustrating. It is the most common joint condition in the world, affecting hundreds of millions of people, and the instinct to protect a sore joint by moving it less is exactly backwards.

Here is the part that gets lost: exercise is not a nice-to-have for knee osteoarthritis. It is the treatment. Clinical guidelines from arthritis organizations across the US, Europe, and the UK all list exercise as a core, first-line intervention, ahead of painkillers and far ahead of surgery for most people. The question was never really whether to exercise. It was which kind, and how much.

For a long time the honest answer to that was "we are not sure." A large 2025 study changed that. This article walks through what the strongest evidence now shows, why aerobic exercise edged out the rest, and how to actually start when your knee hurts.

The Research: What Studies Show

The 2025 BMJ Network Meta-Analysis

The single most useful study on this question came out in 2025. Yan and colleagues (2025), publishing in The BMJ, ran a systematic review and network meta-analysis of 217 randomized controlled trials covering 15,684 people with knee osteoarthritis. A network meta-analysis is powerful because it does not just ask "does exercise beat doing nothing." It ranks different exercise types against each other, even types that were never compared head-to-head in a single trial.

The headline finding: aerobic exercise was likely the most beneficial modality, with moderate-certainty evidence. It produced large improvements in pain in the short and medium term, with standardized mean differences around -1.10 and -1.19 versus control. It also led the field for function, gait performance, and quality of life. Across outcomes, aerobic exercise had the highest probability of ranking as the best option, with a mean ranking-curve value of about 0.72.

"Aerobic exercise" here means rhythmic, continuous activity that raises your heart rate: walking, stationary cycling, water-based exercise, light dancing. Not sprinting, not heavy lifting. The kind of movement most people can do at home or in a pool without special equipment.

The Cochrane Review: Exercise Reduces Pain, Reliably

The 2025 paper built on a deep foundation. The benchmark reference before it was the Cochrane review by Fransen and colleagues (2015), which pooled 54 trials of land-based exercise for knee osteoarthritis. That review found moderate-quality evidence that exercise reduces knee pain right after a program ends, and improves physical function, with a low rate of adverse events.

One detail from the Cochrane review matters more than the average reader expects: the benefit faded. Pain relief and function gains were still present 2 to 6 months after the program, but shrinking. Exercise for knee osteoarthritis behaves less like a course of antibiotics and more like brushing your teeth. It works while you keep doing it.

The FAST Trial: Both Aerobic and Strength Work

Long before the meta-analyses, one landmark trial set the tone. Ettinger and colleagues (1997) ran the Fitness Arthritis and Seniors Trial, published in JAMA. They randomized 439 adults aged 60 and older with knee osteoarthritis into three groups: aerobic walking, resistance exercise, or a health education control. Over 18 months, both exercise groups showed modest but real improvements in pain, physical disability, and performance measures like walking distance and stair climbing. The education-only group did not.

That trial established a principle the 2025 data refined rather than overturned: more than one kind of exercise helps. Aerobic work may rank first now, but resistance training was never the wrong answer. It was a good answer.

Why Aerobic Exercise Came Out on Top

The 2025 ranking surprised some clinicians, because knee osteoarthritis advice has leaned hard on quadriceps strengthening for decades. The logic seemed airtight. Weak thigh muscles, painful knee, so build the muscle and unload the joint. So why did walking and cycling outrank it?

A few reasons. Aerobic exercise does more than work the joint locally. It improves cardiovascular fitness, supports modest weight loss, lifts mood, and reduces the low-grade systemic inflammation linked to osteoarthritis pain. Knee osteoarthritis pain is not purely mechanical. It is shaped by inflammation, body weight, sleep, and how the nervous system processes pain signals. Aerobic exercise touches several of those levers at once.

There is also a sharper point hiding in the strengthening research. Bartholdy and colleagues (2017) ran a meta-regression specifically asking whether the programs that built the most quadriceps strength produced the most pain relief. They did not. Programs that followed general exercise dose guidelines did better than programs narrowly focused on maximizing thigh strength. The takeaway is subtle but important: the pain relief seems to come from the act of regular exercise itself, not from hitting a specific strength number.

So the practical reading of the 2025 data is not "stop strengthening your legs." It is "do not skip exercise because you cannot do a structured strength program." Walking counts. Cycling counts. The pool counts.

How Exercise Helps a Joint That Already Hurts

It feels counterintuitive to load a joint that grinds and aches. Understanding why it helps makes it easier to push through the first uncomfortable weeks.

Cartilage has no direct blood supply. It is fed by joint fluid, and that fluid only circulates through the cartilage when the joint moves and is gently loaded. A knee that rarely bends and straightens is a knee whose cartilage is poorly nourished. Movement is, quite literally, how the joint stays fed.

Exercise also strengthens the muscles that share load with the joint, improves the proprioception that keeps the knee tracking properly, and reduces the joint stiffness that makes the first movements of the day so unpleasant. And it changes how the nervous system handles pain. Regular exercise produces a measurable, short-term reduction in pain sensitivity, an effect researchers call exercise-induced hypoalgesia. The knee may not look different on a scan, but it can hurt meaningfully less.

This is also where the fear of "wearing the joint out" needs to die. Moderate, regular exercise is not associated with faster cartilage loss in people with knee osteoarthritis. The cost runs the other way. Inactivity weakens the muscles around the knee, stiffens the joint, drives weight gain that loads the knee further, and raises cardiovascular risk. If you have read our guide on staying active with joint pain, this is the same principle: protected joints get weaker, not safer.

What an Effective Program Looks Like

One of the best-studied real-world programs is GLA:D, short for Good Life with osteoArthritis in Denmark. Skou and Roos (2017) reported outcomes for 1,045 patients with knee and hip osteoarthritis who went through it. The structure is simple: a couple of education sessions about the condition, then supervised neuromuscular exercise twice a week for about six weeks. At the three-month follow-up, patients reported less pain, used fewer painkillers, took less sick leave, and walked faster.

You do not need to enroll in a formal program to borrow its shape. A sensible at-home week, built from the research, looks like this:

• Aerobic base, most days. Aim toward 150 minutes a week of moderate aerobic activity, broken into chunks you tolerate. Walking, stationary cycling, or water exercise. Three 10-minute walks count the same as one 30-minute walk.
• Lower-body strengthening, 2 to 3 times a week. Bodyweight or resistance-band work for the quads, glutes, and calves: sit-to-stands from a chair, gentle step-ups, wall sits, bridges. No heavy weights required.
• Balance and mobility, woven in. Single-leg stands near a counter, gentle range-of-motion work, and stretching reduce stiffness and the fall risk that comes with an unsteady knee.
• Progress slowly. Add a little time, distance, or repetitions roughly every one to two weeks, not every session.

The pain rule that keeps people safe and consistent: activity-related discomfort up to about 5 on a 0-to-10 scale is acceptable, as long as it settles back to your normal baseline within 24 hours. If a session leaves your knee flared for two days, that session was too much. Scale it back, do not stop. For more on building the habit when it is not comfortable yet, our guide on staying fit over 60 covers the consistency side in depth.

Common Misconceptions

Misconception 1: "Exercise will wear my knee out faster."

The opposite is closer to the truth. Moderate exercise is not linked to accelerated cartilage breakdown, and it is recommended as first-line treatment precisely because the joint does better with regular, well-dosed movement. The activity that does load the joint badly is not exercise. It is carrying extra body weight on a sedentary, weak-muscled frame. Strong muscles and a regular movement habit protect the knee. Avoidance erodes it.

Misconception 2: "I should wait until the pain is gone to start."

If you wait for a pain-free knee, you may never start, because exercise is part of what brings the pain down in the first place. Trials enroll people who already have knee pain, and those people improve. The goal is not to exercise a perfect knee. It is to exercise the knee you have, within a sensible pain limit, and let the pain ease as fitness builds.

Misconception 3: "Only strengthening exercises help knee arthritis."

This was the conventional advice for years, and it is not wrong, just incomplete. The 2025 BMJ analysis ranked aerobic exercise first. Strengthening still helps. So do neuromuscular, balance, and mind-body approaches like tai chi. The strongest evidence-based message is not "pick the one correct exercise." It is "pick something aerobic-leaning you will actually repeat, and add strength work when you can."

What the Research Suggests Going Forward

The evidence here is unusually consistent for an exercise-science topic. Across a 1997 landmark trial, a 54-study Cochrane review, and a 217-trial network meta-analysis, the direction never changed: exercise reduces knee osteoarthritis pain and improves function, and it is safe to do with a sore knee.

What the 2025 data added is a useful tiebreaker. When someone with knee osteoarthritis asks "what should I do first," the best-supported answer is now aerobic exercise: walking, cycling, or pool work. But the honest framing matters. The gap between aerobic and strength exercise is small. The gap between exercising and not exercising is large. Certainty in the research is rated moderate, not high, partly because exercise trials cannot be blinded and adherence varies a lot.

Which points at the real challenge. The science of what to do is largely settled. The unsolved problem is consistency: the Cochrane data is blunt that benefits fade within months once exercise stops. Knee osteoarthritis is a long game, and the people who do best are not the ones who found a perfect protocol. They are the ones who kept a good-enough routine going. That is also the thread through our piece on strength training after 60: the program only works if it is still happening a year from now.

References

1. Yan L, Li D, Xing D, et al. "Comparative efficacy and safety of exercise modalities in knee osteoarthritis: systematic review and network meta-analysis." BMJ. 2025;391:e085242. doi:10.1136/bmj-2025-085242
2. Fransen M, McConnell S, Harmer AR, Van der Esch M, Simic M, Bennell KL. "Exercise for osteoarthritis of the knee." Cochrane Database Syst Rev. 2015;1:CD004376. doi:10.1002/14651858.CD004376.pub3
3. Ettinger WH, Burns R, Messier SP, et al. "A randomized trial comparing aerobic exercise and resistance exercise with a health education program in older adults with knee osteoarthritis. The Fitness Arthritis and Seniors Trial (FAST)." JAMA. 1997;277(1):25-31. doi:10.1001/jama.1997.03540250033028
4. Skou ST, Roos EM. "Good Life with osteoArthritis in Denmark (GLA:D): evidence-based education and supervised neuromuscular exercise delivered to 1,045 patients with knee and hip osteoarthritis." BMC Musculoskelet Disord. 2017;18(1):72. doi:10.1186/s12891-017-1439-y
5. Bartholdy C, Juhl C, Christensen R, Lund H, Zhang W, Henriksen M. "The role of muscle strengthening in exercise therapy for knee osteoarthritis: A systematic review and meta-regression analysis of randomized trials." Semin Arthritis Rheum. 2017;47(1):9-21. doi:10.1016/j.semarthrit.2017.03.007