Tiny Squat Mistake Wrecking Knees

A common squat habit is quietly wrecking knees, and fitness coaches say one simple fix can stop it.

Quick Take

Coaches call the mistake “valgus collapse,” when knees cave inward during a squat.
A widely viewed fitness video explains why this happens and how to correct it.
Multiple trainers and a medical group agree: knees should track over the toes, not fall inward.
Research reviews show the picture is more complex, depending on depth, stance, and individual injury history.

The Mistake Behind the Warning

A new fitness video warns that many people think they are squatting correctly, but they are actually hurting their knees. The video names the problem: “valgus collapse.” That’s when the knees cave inward toward each other instead of staying lined up with the toes. The creator says this happens during everyday squats, not just gym workouts.

Other fitness channels describe the same issue using different words. One video calls it “the most common mistake I see people make when they’re standing up from a chair or doing a squat,” pointing out that knees “cave in” as people rise. Another channel lists knee cave as one of five mistakes that can damage both knees and the lower back over time.

How Trainers Say to Fix It

The fix starts with foot position. The video recommends a slightly wider stance with toes turned out a bit before bending the knees. A fitness company called WeShape publishes similar advice in a blog post, telling readers to “activate your feet,” then “press your knees outward slightly” while keeping knees aligned with the toes. The goal is to engage muscles on the outside of the hips instead of letting the knees drift inward.

A medical group that treats knee injuries backs up this basic idea. Wisconsin Medical Group lists failing to turn the knees out as one of the biggest squat mistakes people make. The group also warns that letting knees collapse inward can shut down the glute muscles and cause lasting knee damage. Several other trainers point to the same rule: knees should travel in the same direction as the toes throughout the movement.

It’s Not Just About the Knees

Trainers say knee position is only part of the problem. One video points out that many people shift their weight forward onto their toes instead of keeping it back on their heels, which throws off balance and adds stress to the joints. Another instructor notes that people often let their knees drift too far forward while also losing proper pelvic and back position as they squat.

These smaller mistakes add up. A stance that’s too narrow, toes pointed the wrong way, or weight sitting in the wrong spot on the foot can all make knee cave worse, according to the trainers reviewed. That’s why most fixes involve checking foot position first, then knee alignment, rather than treating knee cave as an isolated problem.

What the Research Says

Scientific reviews of squat mechanics generally agree that letting the knees fall inward is linked to knee pain and injury risk, especially in movements like the single-leg squat used in physical therapy testing. Studies on patellofemoral pain, a common form of kneecap pain, found people with symptoms showed noticeably more inward knee movement than pain-free people during single-leg squats.

Researchers also caution that squat safety depends on more than one fix-all cue. A widely cited biomechanics review found stance width, depth, and the phase of recovery all change how the knees behave, meaning advice that works for one person may not fit another. A strength and conditioning journal similarly concluded that current evidence supports a natural foot stance about shoulder-width apart, with the knees allowed to move forward naturally rather than forcibly held back.

Together, the trainer advice and the research point in the same direction. Watching where the knees travel during a squat, and keeping them tracking with the toes, remains one of the simplest ways to protect the joint. For the millions of people who squat daily without thinking about form, that small adjustment could mean the difference between building strength and slowly wearing down the knees.