Knee pain when squatting or lunging: causes and how to train around it

Pain around or behind the kneecap, worse going down stairs, sitting for long with the knees bent, or at the bottom of a squat, is usually patellofemoral pain: the kneecap and the groove it runs in are irritated by more load than they are used to.

Pain just below the kneecap, in the tendon, worse with jumping, lunges or the start of a squat, is usually patellar tendinopathy, sometimes called jumper's knee.

Pain on the inner or outer side of the knee joint, especially after a twist, with clicking, catching or the knee locking, can mean a meniscus problem and needs assessment before heavy squatting.

Too much, too soon. Adding a lot of squat volume or weight in a few weeks, or starting a new programme with leg press, lunges and squats all at once, is the most common cause.

Knees collapsing inward as you come up, often because the hip muscles are weak or the stance is too narrow. Pushing the knees out in line with the toes usually helps.

Very deep squats before the ankles and hips have the movement for them, so the knees and lower back make up the difference. Squatting to a depth you control is fine; depth can come later.

Lots of knee-dominant work with little for the hips and hamstrings. A programme of squats, leg press and leg extensions with no hip hinges or glute work loads the front of the knee heavily.

Use the same pain rule as for tendons: pain up to about 3 out of 10 during the exercise that settles by the next day is acceptable. More than that, or a knee that is worse the next morning, means reduce the load.

Reduce depth for now, for example squat to a box, and slow the lowering phase. Swap lunges and jumping for split squats with a hand on support, and replace leg extensions with exercises the knee tolerates.

Strengthen the hips and the back of the thigh: bridges, side-lying leg raises and hamstring work spread the load away from the front of the knee. Calf and ankle mobility helps people who cannot squat without the heels lifting.

Once a squat to a comfortable depth is pain-free, increase depth first, then load, a little each week. For tendon pain, slow heavy squats and split squats usually help more than light high-repetition work.

Expect six to twelve weeks for tendon pain to settle fully. Kneecap pain often eases faster once the load is right.

A knee that swells within hours of a twist, gives way, or locks and will not straighten needs assessment for a ligament or meniscus injury.

Severe muscle pain and swelling after an unusually hard leg session, especially with dark or cola-coloured urine, can be rhabdomyolysis, a serious muscle breakdown that affects the kidneys. It is seen in new gym members who do too much too soon. Go to a hospital the same day.