Knee pain is one of the most common things people ask about — roughly one in three adults gets it at some point. This page is the map: what tends to be going on, what genuinely needs checking, where to start, and which guide to read for your particular version of it.
The short version
- Most everyday knee pain is around or behind the kneecap. Clinicians call it patellofemoral pain.
- It usually means the knee has become sensitive to load — not that something is broken.
- Building up the thigh and hip muscles is the best-supported starting point.
- A handful of symptoms — locking, giving way, a hot swollen knee, injury — need looking at in person first.
What most knee pain actually is
The knee is a hinge that also has to absorb load, and it does that job with the help of the muscles around it. When those muscles can't quite handle what you're asking, more of the work lands on the joint itself, and the area gets irritable.
That irritability has a name. Pain around or behind the kneecap is called patellofemoral pain, and the NHS describes it as pain that flares with stairs, squatting, kneeling and long periods of sitting. It's the single most common pattern, and it typically shows up without any obvious change in the structure of the joint. Nothing is visibly broken. The knee has just become sensitive.
Why now? Usually because something changed. More steps, a new sport, a return after time off, a heavier gym week, a new job with more sitting or more standing. Knees adapt to what you ask of them, but they adapt slowly, and pain often turns up when the ask jumps faster than the adaptation.
⚠️ When to get your knee looked at in person
Get seen urgently if the knee is badly swollen, hot, red or out of shape, if you have a fever with a hot swollen knee, if you can't put weight on it, or if the leg feels numb, cold or looks pale.
- Book an appointment if the knee locks, catches, gives way, or won't straighten
- Book an appointment if the pain started with a fall, a twist, or a "pop"
- Book an appointment if the pain is severe, worsening over weeks, or waking you at night
- Book an appointment if you also have unplanned weight loss, night sweats, or feel generally unwell
Everyday activity-related knee pain with none of these is far less concerning.
Find your version of it
Knee pain behaves differently depending on what sets it off, and the detail matters more than the label. Pick whichever sounds most like yours.
Pain on stairs
- Knee pain when going downstairs — the most common version. Why lowering loads the kneecap hardest, and the starter routine.
- Why does my knee hurt only on stairs? — what it means when flat ground is fine but stairs aren't.
- Knee pain going up stairs but not down — why one direction can hurt while the other doesn't.
- Knee feels unstable going downstairs — the difference between feeling wobbly and actually giving way.
Pain from sitting, or from being active
- Knee pain after sitting cross-legged — the "cinema sign", and why moving fixes it.
- Runner's knee — when running or a jump in mileage is the trigger.
- Knee pain in your 30s — why being young is reassuring, not alarming.
Noises, without pain
- Knee clicking with no pain — what the research says about crepitus, and when the noise actually matters.
Where to start, whichever version you have
The common thread across all of them is the same: build up the muscles around the knee and hip. Physiotherapy guidelines (JOSPT) back working the hip and knee together rather than the knee alone. These are the two exercises worth learning properly first.
A hold, so the muscle works while the joint stays still — often comfortable when moving exercises are sore. Full instructions.
Trains the exact control stairs demand. Start ankle-height and lower slowly. Full instructions.
From a firm chair, stand and sit slowly, about three seconds each way. Knee tracking over your middle toes.
Lie on your side, knees bent, feet together. Lift the top knee and lower slowly. Strong hips help the knee.
Mild discomfort during and just after is fine. Sharp pain, or soreness that's clearly worse the next day, means do less next time — not stop altogether.
How long it takes
Longer than most people expect, and that's normal. NHS advice for front-of-knee pain suggests it can take up to about 12 weeks of regular exercise before you see a clear change. Add a little each week — more repetitions first, then slower movements, then harder versions — and judge it after a couple of months rather than a fortnight.
Consistency matters more than intensity. A little most days beats an occasional hard session.
The bottom line
Most knee pain is a knee that's become sensitive to load rather than a knee that's damaged, and steady thigh and hip work is what shifts it. Find the guide above that matches how yours behaves, give it a couple of months, and get it looked at in person if the knee locks, gives way, swells, or the pain started with an injury.