Runner's knee after 40: which knee pain you actually have

You felt it on the stairs when you got home. Or it started as a nagging point at kilometre four that vanished the moment you stopped, and now it shows up earlier every time. The first thing you did was search for it. That is where the trouble starts, because the term you almost certainly searched for does not point at one single thing.

The name is unreliable. The location is not.

This is not pedantry about words. It explains why the advice you find contradicts itself.

In English-language medical sources, runner's knee generally means patellofemoral pain: pain at the front of the knee or around the kneecap, made worse by running, jumping, kneeling, squatting, climbing stairs and sitting for long periods with the knees bent. That is the standard usage from institutions like Johns Hopkins Medicine and the American Academy of Orthopaedic Surgeons.

In everyday use, though, the same phrase gets attached to almost any knee that hurts when you run. And the second most common running knee problem sits somewhere else entirely. Iliotibial band syndrome involves the thick band of connective tissue running down the outside of the thigh to the knee. It produces pain on the outside of the joint, and it behaves differently: it tends to show up partway into a run and then build, and it can settle after a few days of rest.

How far apart are these two usages? Far enough that a national health service uses the term the other way round. Sweden's public health information service, 1177, has a page whose title translates directly as runner's knee, and it describes the tendon along the outside of the knee becoming overloaded, with pain that can be sharp, that arrives during the session and increases as the session goes on. Same name, other side of the knee.

How to tell which one you have

The two problems have different signatures. They differ not just in location but in when they hurt, which is often the clearer clue.

Two details from the 1177 guidance are easy to miss. Running downhill and on sloping or cambered ground raises the risk of the outside-of-knee problem. And running is not the only cause: cycling and cross-country skiing can produce it too, with skate skiing being the usual skiing trigger. If you run the same loop every day along a road edge that slopes consistently, or always the same direction around a track, that is worth looking at before you change anything else.

This is general health information, not a diagnosis. Both problems can coexist, and there are more causes of knee pain than these two. A physiotherapist can usually work out which is which in a few minutes, which is worth more than an hour of reading.

What the research says about why it happened

Knees account for a large share of running problems. A 2026 systematic review in the Orthopaedic Journal of Sports Medicine reports that knee injuries make up 25 to 30 percent of all running-related injuries. The three most commonly reported are patellofemoral pain syndrome, iliotibial band syndrome and patellar tendinopathy.

That review screened 1,883 articles down to 20 studies and looked for what actually predicts a knee injury. Two factors dominated:

• Previous injury. Odds ratios ranged from 1.36 to 10.19. For knee injuries in general, previous injury was the most frequently reported risk factor, associated with a 12.9 percent higher incidence of reinjury.
• Increased training load or volume. Odds ratios ranged from 1.07 to 8.94.

Structural malalignment also featured, with odds ratios from 1.89 to 4.12. For the outside-of-knee problem specifically, the strongest reported associations were movement variables rather than mileage: kinematic factors with odds ratios from 3.02 to 5.62, and a kinetic factor at 8.88, reflecting abnormal pelvic motion and impaired shock absorption.

Notice what is not on that list: your age. It is the explanation you are most likely to be offered at 45 ("well, you are not twenty any more") and the least well supported. What predicts a painful knee is what you have hurt before and what you did in the last few weeks.

The gap worth knowing about

Here is a detail that almost never gets written down, and it applies specifically to readers over 40. The review above is the most recent synthesis of risk factors for runners' knee problems. Its methods section states that studies were excluded if they focused on athletes older than 30.

So the risk-factor picture for knee injuries in runners is extrapolated from a population younger than this article's reader. That does not make it useless: tendons and load do not start behaving differently on your fortieth birthday. But it does mean anyone claiming the research shows exactly what applies to a 47-year-old knee is saying more than the evidence supports. The honest version is that the two strongest factors, injury history and load increases, are well established in younger groups, while the effect of age itself has not been mapped the same way. The review is also graded level 3 evidence, which is not the strongest design available.

In practice this matters less than it sounds. Look at your own last four weeks: a new longest run, more sessions, more hills, a new surface, or speed work added in the same week the volume went up. That is where the answer usually sits. How to add distance without ending up here is covered in the guide on running 10K.

No, recreational running does not wear out your knees

This fear sits underneath almost every case of knee pain after 40, so it deserves a straight answer with numbers.

A systematic review and meta-analysis published in 2017 in the Journal of Orthopaedic & Sports Physical Therapy pooled 25 studies covering 125,810 people, of which 17 studies with 114,829 people went into the meta-analysis. Prevalence of hip or knee osteoarthritis broke down like this:

Recreational runners came out lower than both the elite group and the sedentary group. An overview of the evidence published in 2022 in the European Journal of Rheumatology, built on 20 reviews plus 12 original studies, points the same way: common forms of physical activity, including walking and running, are not related to structural progression of knee osteoarthritis, and can be safely recommended to people who have or are at risk for it.

Two honest caveats. The authors of the 2017 review state plainly that they could not determine whether the associations are causal. Healthy knees make it easier to keep running for twenty years, so some of the gap may run in that direction. And the elite figure shows the picture reverses at very high volumes and intensities sustained over years. If you run three to five times a week, the middle row is yours.

The first two weeks: what you actually do

What turns a two-week problem into a three-month problem is nearly always continuing to run as usual in the hope that it settles. Here is the starting point, with the 1177 self-care guidance as the basis for the outside-of-knee problem.

If it hurts on the outside

1177 states that you usually recover from this problem by resting for a few days and then training with less load, shorter duration or lower intensity than before, and that you may need to switch to a form of training that puts less load on the tendon. Over-the-counter painkillers can be used if the pain is bad, though usually no medication is needed. Symptoms may resolve faster if you stretch and get treatment from a physiotherapist, naprapath or chiropractor.

Translated into a week in your calendar:

• Days 1 to 4: no running. Walk if walking is painless.
• Remove the trigger first. Downhills and cambered ground are named risk factors. Change the route before you change anything else, and stop running long stretches along the same sloping road edge in the same direction.
• Restart at half: half the time you were running, easy pace, flat ground. If three sessions feel fine, change one variable.
• Cross-train meanwhile with something that does not produce pain. Note that 1177 names cycling and skate skiing as possible triggers of this specific problem, so the bike is not automatically the safe option. Swimming or walking is more often the safer option.

If it hurts at the front

The principle is the same, less load for a period plus targeted strength work, but the triggers to remove are different. Here it is stairs, deep squats, downhill running and long spells sitting with bent knees that tend to provoke it. Two things that usually help: shorten the sessions rather than stopping outright, and swap the steep descent in your loop for a flatter road. Downhill running produces high load peaks across the kneecap joint.

On the rehab exercises themselves, it is worth knowing what the evidence base actually looks like. A 2025 systematic review in Frontiers in Rehabilitation Sciences examined 79 studies of knee extensor training for patellofemoral pain. The most commonly prescribed exercises were the straight leg raise, the squat and open-chain knee extension, typically three sets of ten repetitions using bodyweight resistance. The authors conclude that this training is predominantly low-load and moderate-volume, differing from conventional strength training recommendations, and that intensity and range of motion are often reported too poorly to reproduce the protocols. In other words: start light, because light is what has been tested. Do not assume you need a loaded barbell for it to count.

Strength: the one thing with meta-analytic support

If you do one thing beyond reducing the dose, do this one. The reason is that the gap between the available options is much larger than most coverage admits.

A 2014 meta-analysis in the British Journal of Sports Medicine included 25 randomised trials with 26,610 participants and 3,464 injuries. By intervention:

Read that bottom row again. A risk ratio of 0.963 with a confidence interval crossing 1 means no demonstrated preventive effect from stretching. Strength training sat at 0.315. For overuse injuries specifically, the category both of these knee problems belong to, the risk ratio was 0.527.

A 2018 follow-up review by the same lead author found a risk ratio of 0.338 and identified a dose response: a 10 percent increase in strength training volume reduced injury risk by more than four percentage points. Formal tests found no publication bias, and the strength of evidence was rated high.

What you do about it: two short sessions a week covering glutes, hips, the front and back of the thigh, and the calves. Twenty minutes on the floor at home is enough to start, and the structure is in the guide on strength training at home. How to fit strength and running into the same week without one eating the other is covered in the guide on strength training and running.

What helps less than you hope

• Stretching as protection. See the table above. As treatment for an existing outside-of-knee problem, 1177 does recommend it, alongside treatment from a physiotherapist, naprapath or chiropractor. Those are two different questions with two different answers, and they are easy to conflate when reading quickly.
• A new shoe. No shoe makes you injury-proof. A shoe that feels comfortable and that you are used to is a sensible choice. Switching model in the middle of an active problem adds a new variable exactly when you want fewer.
• Weeks of complete rest. Rest for a few days is the guidance, then training at lower load. Passive rest with nothing else changed often leads straight back to the same pain on restart, because none of what caused it has been addressed.
• Running through it. Pain that makes you limp or that builds during the session is information, not something to negotiate with.

When to get it looked at

See your doctor or a physiotherapist if the symptoms are not resolving. In many countries you can go directly to a physiotherapist without a referral.

Get assessed sooner, without waiting it out, if any of these apply:

• The knee swells rapidly, gives way, locks or feels unstable.
• You cannot put weight on the leg, or you are limping in daily life.
• It started with a twist, a fall or a blow.
• The knee is red and swollen and you have a fever.
• The pain wakes you at night or is present at complete rest.
• You have numbness or weakness in the leg or foot.

Operatör 45 provides general health information. We do not diagnose and we do not give personal medical advice. Nothing here replaces an assessment by a physiotherapist or doctor, and when in doubt that assessment is always the right call.

The way back

The most common mistake after three pain-free weeks is returning to the week that caused the problem. Your body has been unloaded. That week was too much when you were in form.

Build up as if you were starting over, just faster. A reasonable structure:

The rule that holds throughout: one thing at a time. Volume, hills and speed are three different loads, and combining two of them in the same week is the classic route back into this article. Keep the easy runs genuinely easy, at the pace described in the guide on zone 2, and the week will tolerate more. If you are rebuilding from the ground up, the full on-ramp is in the guide on starting to run after 40.

A missed session is data, not a failure. A knee that complains in week six is not a sign that you are too old for this. It is a sign that week five was too fast, which is the most fixable cause there is.

Frequently asked questions

What is runner's knee exactly?

In English-language medical sources, runner's knee usually means patellofemoral pain: an ache at the front of the knee, around or under the kneecap, that gets worse with stairs, squatting, downhill running and sitting for a long time with bent knees. But the same name is often applied loosely to any knee pain in runners, including iliotibial band syndrome, which sits on the outside of the knee and behaves differently. Sweden's national health information service, 1177, uses its version of the term specifically for the outside-of-knee problem. Because the label is unreliable, start with the location of the pain rather than the name.

Can I keep running with runner's knee?

Often you can run less rather than stop completely, but not the way you were running. The self-care guidance from 1177 for the outside-of-knee problem is to rest for a few days and then train with less load, shorter duration or lower intensity than before. You may also need to switch to a form of training that puts less load on the tendon. The practical limit: pain that makes you limp, that builds during the session, or that is still there the next day means the dose is still too high. Running through that kind of pain almost always makes the story longer.

Does running wear out your knees?

There is no support for that when it comes to recreational running. A systematic review and meta-analysis of 25 studies covering 125,810 people found the prevalence of hip or knee osteoarthritis was 3.5 percent in recreational runners, 10.2 percent in sedentary controls and 13.3 percent in competitive elite runners. The authors were explicit that they could not determine whether these associations are causal, since healthy knees make it easier to keep running. But the picture of recreational running grinding down knees is not what the data shows.

Does stretching help?

Two different questions with two different answers. As prevention, stretching has not been shown to work: in a meta-analysis of 25 trials with 26,610 participants, stretching came out at a risk ratio of 0.963, which is essentially unchanged risk. As treatment for an outside-of-knee problem that already exists, 1177 states that symptoms may resolve faster if you stretch and get treatment from a physiotherapist, naprapath or chiropractor. So stretch if your knee hurts on the outside, but do not count on stretching to protect you from the next episode.

When should I see someone about knee pain?

See your doctor or a physiotherapist if the symptoms are not resolving. Get assessed sooner, without waiting it out, if the knee swells rapidly, gives way or locks, if you cannot put weight on the leg, if it started with a twist, a fall or a blow, if the knee is red and swollen and you have a fever, if the pain wakes you at night, or if you have numbness or weakness in the leg or foot.

Why now, after months without any problem?

Look at the four weeks before the pain, not the day it appeared. In the research on knee injuries in runners, two factors come up more strongly than any others: previous injury and increased training load. Common triggers are a new longest run, more sessions per week, more downhill or cambered ground, a change of surface, or adding speed work in the same week you added volume. Age itself is not on the list.

Sources

1177, Löparknä (Sweden's national health information service, last updated 2024-09-12, reviewed by a specialist in general medicine). Common Risk Factors for Knee Injuries in Runners: A Systematic Review, Orthopaedic Journal of Sports Medicine 2026. Alentorn-Geli et al., The Association of Recreational and Competitive Running With Hip and Knee Osteoarthritis, Journal of Orthopaedic & Sports Physical Therapy 2017. Walking, running, and recreational sports for knee osteoarthritis: an overview of the evidence, European Journal of Rheumatology 2022. Lauersen et al., The effectiveness of exercise interventions to prevent sports injuries, British Journal of Sports Medicine 2014, and Strength training as superior, dose-dependent and safe prevention of acute and overuse sports injuries, British Journal of Sports Medicine 2018. Knee extensor training in patients with patellofemoral pain: a systematic review and synthesis, Frontiers in Rehabilitation Sciences 2025. Patellofemoral pain descriptions from Johns Hopkins Medicine and the American Academy of Orthopaedic Surgeons.