Where the pain sits narrows it quickly. Pain at the front, worse on stairs and after sitting, is usually kneecap pain. Pain on the inside with stiffness is usually osteoarthritis or the meniscus. Pain on the outside during running is usually the IT band. Fullness behind the knee is usually a Baker’s cyst. Get it checked the same week if the knee locks, gives way, swelled within hours, or is hot with a fever.
Where the pain is sharpest specifically on the way down a staircase, the reason that direction is the hardest test a knee faces is explained in PhysioHub’s guide to knee pain going down stairs.
The knee is unusually cooperative about telling you what is wrong, because the four quarters of the joint produce fairly distinct patterns. This is where each one usually leads.
| Where it hurts | Usual cause | Telltale sign | First things that help |
|---|---|---|---|
| Front, around the kneecap | Patellofemoral pain | Worse on stairs and after long sitting | Quad and hip strengthening, adjust squat depth |
| Inside, with stiffness | Osteoarthritis | Stiff first thing, eases with movement | Regular walking or cycling, strength work |
| Inside, after a twist | Meniscal problem | Tender on the joint line, catching or locking | Avoid deep pivoting, graded loading |
| Outside, during running | Iliotibial band syndrome | Comes on at a predictable distance | Cut mileage and downhill running, hip strengthening |
| Behind, feels full | Baker’s cyst | Tightness on bending fully | Treat the underlying joint problem |
Four of these five improve with roughly the same programme of strength work, which is why an exact label matters less in week one than people expect.
Our guide to knee pain treatment covers how an assessment tells these apart and what the programme looks like for each.
This is a documentary review of published evidence and guidance rather than a diagnosis of your knee. The five here are the causes that account for the large majority of non-traumatic knee pain in adults. Others considered and left out because they are less common or need a different pathway include ligament tears, patellar and quadriceps tendinopathy, pes anserine irritation, bursitis, inflammatory arthritis, gout, and referred pain from the hip.
The order reflects how often each explains ongoing knee pain in adults, weighed against how clearly it can be recognised without imaging.
The sources read were the 2024 Cochrane review of exercise for knee osteoarthritis, covering 139 trials and 12,468 participants, NICE guideline NG226 on osteoarthritis, and the 2018 JOSPT meta-analysis of hip and knee strengthening for patellofemoral pain. Evidence checked in August 2026.
What could not be checked: no study has ranked these five by frequency in a UK primary care population, so the order rests on presentation patterns rather than a count. This article does not replace an examination, and four situations override everything in it: a knee that locks, a knee that gives way, swelling that appeared within a couple of hours of an injury, and a hot swollen knee with a fever.
Point to it with one finger. Front, inside, outside or behind separates most of the field before any test is done. A pain you cannot localise, that moves around the front of the joint, is itself typical of kneecap pain.
Notice what provokes it. Stairs and sitting point at the kneecap. Twisting on a planted foot points at the meniscus. A predictable distance into a run points at the IT band. Morning stiffness that eases within half an hour points at arthritis.
Check for mechanical signs. Locking, catching and giving way are the words that change the plan. They suggest something physically interfering with the joint rather than a tissue that is simply overloaded.
Watch the swelling clock. Swelling within two hours of an injury usually means bleeding in the joint, and it is one of the few knee signs that genuinely needs assessing quickly. Swelling that appears the next day is far less alarming.
What it is
Pain arising from the joint between the kneecap and the thigh bone, without any structural damage on imaging. It is also called runner’s knee and anterior knee pain.
Who it affects
Adolescents and adults of any age, more often women, and very commonly runners, cyclists and people who have recently increased stairs, hills or squatting.
How it presents
A vague ache around or behind the kneecap that is hard to point at precisely. Worse going downstairs, squatting, kneeling, and after sitting with the knee bent for a long time. Often a grinding sensation, which on its own means very little.
What the evidence supports
Strengthening is the first-line treatment, and the specific finding worth knowing is that hip work matters as much as knee work. The 2018 meta-analysis by Nascimento and colleagues, pooling 14 trials and 673 people, found combined hip and knee strengthening better than knee strengthening alone for both pain and activity, with the benefit maintained after the programme ended.
What helps
Six to twelve weeks of quadriceps and hip strengthening, reducing the depth of squatting and the amount of stair work temporarily, and raising a bike saddle where cycling is the trigger. Our guide to knee strengthening exercises covers the programme.
Limits and cautions
Complete rest settles it and then it returns, because the underlying capacity has not changed. Grinding noises without pain need no treatment at all.
Why it ranks first
It is the most common cause of knee pain across the whole adult age range, and it is the one most often assumed to be arthritis or cartilage damage when it is neither.
What it is
Wear-related change affecting the cartilage and the bone beneath it, most often in the inner compartment of the knee.
Who it affects
Most commonly people over 50, and earlier after a significant knee injury or a meniscal operation.
How it presents
Pain on the inside of the knee, stiffness first thing that eases within about half an hour, and difficulty with stairs and getting out of low chairs. Swelling that comes and goes. Symptoms fluctuate over months.
What the evidence supports
The 2024 Cochrane review pooled 139 trials and 12,468 participants and found exercise improves pain by about 8.7 points and physical function by about 11.3 points on 100 point scales compared with attention control or placebo. Those are real, modest effects, and exercise plus weight management is what NICE makes the core treatment.
What helps
Regular walking or cycling, leg strengthening two or three times a week, heat for morning stiffness, and weight management where it applies. Expect the first fortnight of exercise to feel worse rather than better.
Limits and cautions
The severity of changes on an X-ray predicts symptoms poorly. Many people with marked changes have little pain and some with minor changes have a lot, which is why treatment decisions are made on how the knee behaves.
Why it ranks second
It is the most common cause of knee pain over 50, and it has the largest body of trial evidence behind its treatment of anything on this list.
What it is
Damage or degenerative change in one of the two C-shaped cartilage pads that sit between the thigh bone and the shin bone.
Who it affects
Two distinct groups: younger people who tear one during a twisting injury, and people over 40 in whom the cartilage gradually frays without a clear injury.
How it presents
Pain along the joint line, usually on the inside, tender to press directly on. Often worse with twisting, squatting deeply or getting out of a car. Catching, clicking or a sense that the knee is momentarily stuck.
What the evidence supports
Degenerative meniscal tears in middle age respond about as well to exercise as to arthroscopic surgery in the trials that have compared them, which has shifted practice substantially over the last decade. Traumatic tears in younger people, particularly those causing true locking, are a different situation and are assessed surgically.
What helps
Avoiding deep pivoting for a few weeks, then graded strengthening of the thigh and hip much as for the causes above. Most degenerative tears settle without an operation.
Limits and cautions
A knee that locks and cannot be fully straightened is the exception, and needs assessing rather than loading. Meniscal changes are found on scans in a large proportion of people over 50 with no knee pain at all.
Why it ranks third
It is common, and it is the diagnosis where the gap between what a scan shows and what needs doing about it is widest.
What it is
Irritation where the thick band of tissue running down the outside of the thigh passes over the outer edge of the knee.
Who it affects
Runners and cyclists almost exclusively, most often after an increase in mileage, a change to hillier routes, or a return to running after a break.
How it presents
Sharp or burning pain on the outside of the knee that comes on at a fairly predictable point in a run, often within the same half mile each time, and eases within minutes of stopping. Downhill running makes it worse.
What the evidence supports
Management centres on reducing the load that provokes it and building hip strength, particularly the muscles controlling how far the thigh drops across the midline. The evidence base here is smaller than for the conditions above and is drawn largely from running populations.
What helps
Cutting mileage temporarily and avoiding downhill and cambered running, alongside hip strengthening for six to eight weeks. Most people are back to full running inside two months.
Limits and cautions
Foam rolling the outside of the thigh is popular and does not change the length of the band, which is not the mechanism anyway. It may make the session more comfortable and it is not the treatment.
Why it ranks fourth
It is common within running populations and uncommon outside them, and it is the most predictable of all these in how it presents.
What it is
A pocket of joint fluid pushed backwards out of the knee capsule into the space behind the joint.
Who it affects
Most often people with osteoarthritis or a meniscal problem, since both produce the extra joint fluid that fills it.
How it presents
A feeling of fullness or tightness behind the knee, worse when bending fully, sometimes with a visible soft swelling. Occasionally it leaks, producing calf pain and bruising that can look alarming.
What the evidence supports
It is a consequence rather than a cause, so managing the underlying joint problem is what settles it. Draining it without addressing the source commonly leads to it refilling.
What helps
Treating the knee problem producing the fluid, which usually means the osteoarthritis or meniscal programme above. Gentle range work keeps the knee moving while it settles.
Limits and cautions
Sudden calf pain and swelling behind the knee can also be a blood clot, which needs excluding urgently. Where calf symptoms appear suddenly, particularly after travel, surgery or immobility, that needs same-day medical assessment.
Why it ranks fifth
It is common as a finding and almost never the actual problem, and it is the one on this list most likely to be worried about more than it deserves.
| Cause | Where it hurts | Worse on stairs | Morning stiffness | Mechanical signs | Typical timescale |
|---|---|---|---|---|---|
| Patellofemoral pain | Front, around the kneecap | Yes, especially down | No, but stiff after sitting | No | 6–12 weeks |
| Osteoarthritis | Inside, deep | Yes | Yes, eases in 30 minutes | Sometimes | Managed long term |
| Meniscal problem | Joint line, usually inside | Sometimes | Sometimes | Catching, locking | 6–12 weeks |
| IT band syndrome | Outside, at the joint edge | No, worse running | No | No | 4–8 weeks |
| Baker’s cyst | Behind, feels full | No | Sometimes | Restricted full bend | Follows the cause |
The mechanical signs column is the one that changes what happens next. Everything else on this table can reasonably be given six weeks of sensible loading first.
If it hurts around the kneecap on stairs and after sitting, that is kneecap pain, and strengthening the thigh and hip over six to twelve weeks is the treatment.
If it is stiff first thing and eases as you move, that pattern points at arthritis. Regular walking and strength work are the core of it, and the first fortnight will feel worse.
If it started with a twist and there is a tender spot on the joint line, treat it as a meniscal problem: avoid deep pivoting for a few weeks and load it gradually.
If it appears at the same point in every run and stops when you do, that is the IT band. Cut the mileage and hills, and start hip strengthening.
If your knee locks, gives way, swelled within two hours of an injury, or you cannot bear weight, get it assessed this week rather than working through it.
If the knee is red, hot and swollen and you feel unwell or feverish, that needs urgent medical assessment the same day.
The belief that walks into the Uckfield clinic most often with a sore knee is that the pain means something inside has worn out, and that a scan will show what. Imaging in this area routinely shows meniscal fraying and cartilage change in people of the same age with no knee pain whatsoever, which is why a report on its own settles very little. It is the reason a scan early in an ordinary knee problem often adds worry without changing the plan.
Preseason at Uckfield Rugby Club and AFC Uckfield is when this shows up most clearly. A run of knee complaints arrives every August and September, and almost none of them are structural. They are knees that spent the summer doing very little meeting three sessions a week, and they respond to load being built rather than investigated. What does change the plan is a knee that locks, gives way, swelled within two hours of a specific incident, or is hot with a fever. Those four are worth acting on quickly, and the rest is usually a capacity problem in disguise.
Where a knee has been sore for more than six weeks without improving, our sports injury and performance service is what separates the four situations above from the many that only need loading properly.
Why does my knee hurt more going down stairs than up?
Going down requires the thigh muscles to work as a brake while the knee bends under your full body weight, which loads the kneecap joint far harder than pushing up does. That is why descending stairs is the movement that most reliably exposes kneecap pain, and why it is often the first thing people notice.
When should knee pain be checked urgently?
The same week if the knee locks and will not fully straighten, if it gives way, if it swelled up within a couple of hours of an injury, or if you cannot put weight through it. Immediately if the knee is red, hot and swollen and you have a fever, which can indicate joint infection. Everything else can reasonably be given a few weeks of sensible loading first.
Does knee pain mean I have arthritis?
Usually not, particularly under 50. Kneecap pain, tendon problems and soft tissue irritation account for a large share of knee pain in younger and middle-aged adults. Even where an X-ray shows arthritic change, that finding is common in people with no knee pain at all, so it explains symptoms only when it fits the clinical picture.
What is a Baker’s cyst?
A collection of joint fluid that has been pushed backwards out of the knee capsule, forming a soft swelling behind the joint. It is a consequence of something else producing extra fluid, usually osteoarthritis or a meniscal problem, rather than a problem in its own right. Treating the underlying cause is what settles it.
Should I rest my knee or keep moving?
Keep moving, with the load adjusted. The Cochrane review of exercise for knee osteoarthritis pooled 139 trials and 12,468 participants and found exercise improves pain and physical function, and exercise is the core treatment NICE recommends. Complete rest reduces the capacity of the muscles supporting the knee, which leaves the same load waiting when you return.
Do I need a scan for knee pain?
Rarely at the start. Most knee problems can be identified from where the pain sits, what provokes it and how the knee behaves on testing. Scans matter where there are mechanical signs such as locking or giving way, after a significant injury, or where symptoms are not improving. Age-related findings on knee scans are extremely common in people without pain.
How long does knee pain take to get better?
Kneecap pain typically responds over 6 to 12 weeks of consistent strengthening. IT band syndrome usually settles in 4 to 8 weeks once running load is adjusted. Osteoarthritis is managed rather than resolved, with exercise programmes producing their benefit over about 12 weeks. A knee that has not begun improving after six weeks of sensible loading is worth having assessed.
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