Knee pain when you squat: what causes it and what to do

If your knee bites at the bottom of a squat, or nags the next day on the way down the stairs, the first question isn't which diagnosis you have. It's whether you can keep squatting. Usually you can — just not with the same weight, the same depth or the same number of sets you did last week.

Most squat-related knee pain isn't torn or worn-out tissue. It's a mismatch: the knee was asked to do more than it could handle that week. So the fix has three parts — take the irritation down, sort out what's driving it, then build back up in steps. The rest of this is those three parts in detail.

Work out which pain you actually have

Different pain needs different handling, so blanket advice is useless. Three patterns cover almost everyone who walks into a gym with a sore knee.

• A dull ache around or under the kneecap. Worse at the bottom of a squat, going down stairs, and after a long stretch sitting at a desk or in the car. This is the common one and it responds well to changing the load.
• A precise, pinpoint pain on the tendon below the kneecap. You know it by the pattern: it warms up and fades during the session, then comes back stronger the next morning. It needs patience and steady work, not rest.
• Sharp pain with swelling, locking, or the knee giving way underneath you. This is the one group that doesn't get "try it lighter". It gets seen by a doctor.

In the first two groups, read on. In the third, skip to the doctor section and come back later.

The usual culprit is dose, not technique

Before you start rebuilding your stance and bar position, look at what your last three or four weeks actually looked like. Knee pain rarely turns up out of nowhere — it usually follows a jump in volume or something new.

The classic triggers: going from nine hard leg sets a week to fifteen, moving from half depth to full depth, adding lunges and jumps in the same week, two long hill walks after a winter indoors, or coming back to the gym with the weights you used before the break. None of those is dangerous on its own. The speed is the problem.

A rule that works in practice: change your weekly hard leg sets by roughly ten to twenty per cent, not double. If you're coming back after time off, use a plan that caps how much you can add before you get carried away — there's more on that in the piece on returning to training after a long lay-off.

Technique: four things that genuinely change how the knee feels

Technique isn't behind every sore knee, but when it is, it's usually one of these four.

1. Heels lifting off the floor. If your heels rise at the bottom, the knee picks up what the ankle can't give. Test it: stand with your toes ten centimetres from a wall and try to touch the wall with your knee without the heel lifting. If you can't, train that position and try shoes with a slightly raised heel.
2. Knees collapsing inwards. Most often on the way up out of the hole with a heavier bar. Set your feet slightly wider, turn the toes out a little, and deliberately drive the knees towards your little toes all the way up.
3. Dropping into the bottom. Falling in and bouncing out puts far higher peak forces through the knee. Count three seconds on the way down for the first few weeks.
4. Depth your hips don't actually have. If your lower back rounds at the bottom, that depth is borrowed, not earned. Stop just above that point. If your lower back starts complaining alongside the knee, see what's typical with lower back pain and what needs checking.

The first ten days: what to actually do

The aim isn't to stop using the knee. It's to keep using it in the range that doesn't hurt. Complete rest almost always brings the same problem back three weeks later.

In practice: keep squatting two or three times a week, but drop to around 50 to 60 per cent of your usual weight and stop at the depth where the pain stays at a mild niggle. A box or bench behind you is the easiest way to keep that depth identical every set.

Do three or four sets of six to eight reps with a three-second lowering phase. If even that's too much, swap the squat for isometrics for the first few days: five sets of a 30 to 45 second hold in a half squat against a wall, with a minute between them.

Exercises that usually help

There's no magic movement, but there is a pattern that works: load the knee in a range that doesn't hurt, hard enough and often enough to matter.

• Wall holds or Spanish squats: 5 x 30–45 seconds, two or three times a week. Often takes the edge off for a few hours afterwards.
• Split squats, half range: 3 x 8 per leg, slow on the way down.
• Step-downs from a 15–20 cm box: 3 x 8–10 per leg, three seconds lowering.
• Leg extensions: 3 x 10–15, only through the part of the range that stays quiet.
• Hamstrings and calves: the lower leg and hamstrings share the work with the knee, and hardly anyone trains them properly. The piece on standing and seated calf raises covers how to do that part right.

Getting back to a full squat

Once three sessions in a row pass without a flare-up, start climbing — one variable per week, never two at once.

Weeks 1–2: add five centimetres of depth. Weeks 3–4: walk the weight back towards your old numbers in ten per cent steps. Weeks 5–6: restore your normal set count, and only then add jumps, sprinting or heavy lunges.

Use three rules to decide whether to keep going: pain during the set stays at 3 out of 10 or below, it settles within 24 hours, and the next morning is no worse than the last one. If one of the three fails, drop back to last week's numbers. The same logic applies more broadly to building load back up after an injury.

When to see a doctor

Get it looked at promptly if the knee swelled within a couple of hours of an injury, if it locks or won't straighten fully, if it gave way underneath you, if you can't put weight through it, or if it's hot and red with a fever.

Book an appointment too if the pain has lasted more than six weeks despite cutting the load, if it wakes you at night, or if you get numbness or weakness running down the leg. Everything here is general training advice, not a substitute for being examined.

Common mistakes

• Rest as the only plan. The pain settles, your strength drops, and the comeback hurts just as much.
• Jumping straight back to the old weight on the first pain-free day. The quickest way to repeat the whole cycle.
• Stretching the quads and nothing else. It feels nice, but it doesn't change how much your knee can tolerate.
• Ten different rehab exercises, none of them hard. Three loaded exercises beat a warm-up dressed up as rehab.
• Painkillers so you can train through it. That switches off the one signal you're using to set the dose.
• Ignoring the fatigue outside the gym. Poor sleep and constantly training to failure change what you can absorb — the article on signs of overtraining covers what to watch for.

Common questions

Should my knees stay behind my toes?

No, and for most people they can't. Knees travel past the toes in any deep squat and every time you walk down stairs. Forcing them back just shifts the load onto your hips and lower back.

Do knee sleeves help?

A sleeve gives warmth and feedback, and for some people it genuinely reduces pain during a set. It doesn't heal anything and it doesn't change what the knee can tolerate — use it as a tool, not a solution.

Do I need to stop squatting altogether?

Rarely. In most cases you do better keeping a lighter version of the squat than dropping it for a month.

Is a clicking or crunching knee a bad sign?

If it doesn't hurt and doesn't swell, noise on its own isn't a warning. Pain and locking are what matter, not the sound.

The short version

• Separate the dull ache around the kneecap and the pinpoint tendon pain from sharp pain with swelling or locking — the last one gets checked.
• The usual cause is a jump in volume, not bad form. Look at your last four weeks first.
• Don't stop: drop to 50–60 per cent of your weight, cap the depth, keep two or three sessions a week.
• Add 5 x 30–45 second isometric holds, single-leg work and calf training.
• Add back one variable per week, using the 3/10 rule and the 24-hour settle test.