Lunge mistakes that wreck your knees

Watch a lunge from the front and the giveaway is a knee that drifts inward toward the midline as you lower, often paired with an ankle rolling in and an arch collapsing. This inward collapse, called knee valgus, puts the joint in a twisted, poorly supported position under load. Done occasionally it is no disaster, but grooving it rep after rep under weight is exactly the kind of thing that leaves knees nagging.

The fix is to keep your knee tracking in line with your foot, roughly over your second and third toes, for the whole rep. Think about pushing your knee out slightly so it does not fall in, and grip the floor with your foot to stop the arch collapsing. Often the real cause is weak or sleepy glutes failing to control the thigh, so strengthening your glutes and practising the cue on lighter sets pays off. If your knee still caves when you add weight, the load is ahead of your control.

This one surprises people. A short, cramped step forces your front knee to travel a long way past your toes to reach depth, which increases the load on the front of the knee, including the joint behind the kneecap. Biomechanics research on the forward lunge has found that stress on that joint climbs as the knee bends deeper, and a very short step puts you into that deep, forward knee position under load.

The fix is to take a longer, fuller step so your front shin can stay closer to vertical and your hips share more of the work. A good target is a step where, at the bottom, your front thigh is roughly parallel to the floor and your front shin is fairly upright rather than jammed forward past your toes. This shifts load off the knee and onto your quads, glutes and hamstrings, which is exactly where you want it. A slight forward knee travel is normal and fine, but a knee shoved far past the toes on every rep is the version worth avoiding.

Lunges reward control and punish carelessness. A common fault is dropping fast into the bottom and either banging the back knee into the floor or slamming into the deep position with the joint taking the impact instead of the muscle. Rushing also feeds the knee cave and the short step problems, because you never give yourself time to position anything.

The fix is to lower under control, taking a beat or two on the way down, and to stop the back knee just short of the floor rather than crashing it in. Keep the movement smooth from top to bottom and back, driving up through your front foot with the whole foot planted. Controlled reps let you feel your quads and glutes working and give your knee time to stay in a good line. If you cannot control the descent, the weight is too heavy.

1. Set a long enough step. Long enough that your front shin can stay fairly upright at the bottom, not jammed past your toes.
2. Lower slowly and in line. Take a beat on the way down, knee tracking over your foot, until your back knee is just above the floor.
3. Drive through the whole front foot. Push up through mid foot and heel with the foot flat, not just the ball of the foot, to bring the hips and glutes in.
4. Keep your torso tall. A slight forward lean from the hips is fine, but avoid collapsing forward, which shifts more load onto the front knee.

Some feeling around the knee during lunges is normal, especially the working burn in the muscles around the joint. Mild, symmetrical stiffness that eases as you warm up is usually nothing to worry about. What you should not train through is sharp, pinching, or one sided pain inside the joint, pain that lingers for days, or swelling afterward. Those are signals to back off and reassess, not badges of a hard session.

If lunges bother your knees even with clean form, you have options rather than a dead end. A reverse lunge, stepping backward instead of forward, keeps the front shin more upright and tends to be gentler on the knee, which is why it is often the friendlier starting point. Reducing depth, lightening the load, and building up your glute and quad strength first all help too. Lunges should build your legs, not aggravate your knees, and if clean, sensible lunging still hurts, it is worth getting individual advice from a physio or doctor rather than pushing on.