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If you are learning to squat and hear conflicting advice online about form this short guide will break down some things for you to be aware of to cut through all the noise out there. This list is based on a larger breakdown we did called "Knees Over Toes: What the Science Actually Says" that breaks down the nuance of how the knees move during the squat and what is problematic vs not. What you are seeing here is the cliff notes version but we highly recommend taking a look at the full article and playing with the simulator it has for visualizing mechanics based on your proportions.
For decades, gym-goers have been told that letting their knees travel past their toes is dangerous. Science has proven this false, with several caveats that we will mention later. When you artificially freeze your knees to keep them behind your toes, the physical force doesn't disappear, it shifts directly into your lower back and hips. Natural forward knee travel is completely safe for healthy joints. For most people with adequate ankle mobility, the tibia (shin) will travel forward and place the knee directly over the toes. With the right proportions, your knees may go over your toes, but so long as your heels are flat this really isn't seen as an issue. Without adequate ankle mobility your heels will have to lift up to compensate. This puts you more on your toes and your knees move forward over the toes in the way that people are warned to avoid which can absolutely cause knee pain.
For a full breakdown on how this affects your body, see the complete article.
While most people are similar within a given range in regards to their bone structure, not everyone is built to squat the exact same way. Your limb lengths add nuance to how your squat will look:
Stop trying to copy the exact posture of someone with a different skeleton! Our full article has an interactive tool that lets you manipulate the proportions of an armature to visualize how long thigh bones, short thigh bones, tibia length and torso length change your mechanics.
While forward knee movement can be healthy, doing it by peeling your heels off the ground is a major mistake that indicates a lack of ankle mobility. If your heels lift, it means your ankles lack range of motion in a joint action called dorsiflexion. In basic terms dorsiflexion is the ability to point your toes up which reduces the angle between the ankle and the tibia. If you can't close that angle, you can't squat flat footed and you are shifting into a highly unstable position.
Forward motion is perfectly fine within a certain threshold, but side-to-side motion is a problem if it happens consistently. If your knees cave inward toward each other (a flaw called knee valgus) as you descend into a squat, you are putting stress on the structures of your knee which will lead to irritation in time. This usually points to weak hip muscles, especially the gluteus medius. While not about squatting specifically, this article about fixing low back pain addresses these hip muscles and can help with knee valgus in squatting assuming it is being caused by weak hip muscles.
Where you place the barbell changes how your body needs to move:
It's not uncommon for beginners to try to mix and match these on accident. For example, a high bar back squat with a pronounced hip hinge will lead to more stress on the neck and mid back because the bar position is supposed to nautrally lend itself to a more vertical squat.
Is it safe for my knees to go over my toes when I squat? Yes. For individuals with healthy joints, allowing your knees to track forward naturally over your toes is completely safe so long as your feet stay firmly planted. The human knee is designed to handle these forces. If your heels come up then you are placing undue stress on your knees.
Why do trainers still say to keep knees behind toes? It is an outdated coaching habit that oversimplifies the nuance of biomechanics. Originally meant to reduce stress on the knee joint, researchers now know that restricting the knees actually transfers harmful shear forces directly to your lower back. Find the references in our full article linked above.
What should I do if my heels lift during a squat? Heels lifting usually indicates tight ankles that specifically lack dorsiflexion. You should work on ankle mobility stretches. In the short term, you can safely place small weight plates or wedges under your heels to maintain a stable, flat-footed base. We have a series of mobility articles in the pipeline and should be out in the coming months.
Why does my lower back hurt when I squat? Back pain during squats can happen for a variety of reasons. In context to what we talked about here if you are trying too hard to keep your knees behind your toes it can force you to push your hips unnaturally far back, putting excessive strain on your lumbar spine. This happens when mismatching the squat style and your natural proportions too like trying to hip hinge like you would with a low bar squat with a high bar placement. Sometimes compression of the spine can be an issue in which case other variations like belt squats could be a good choice. Other bars can help too. Safety bars place the load even further down the spine than what you can achieve with a low bar squat with a traditional barbell.
Does my height or leg length affect my squat form? Yes. Your torso length and femur-to-tibia ratio (the length of your thigh bone versus your shin bone) dictates asepcts of your form. People with longer femurs typically have more of a forward lean, while those with shorter femurs can easily maintain a vertical torso.
Should I stop squatting if my knees hurt? If squatting is causing you joint pain, you should pause and consult a physical therapist. Pain is an indicator of an underlying issue, such as a significant mobility restriction or strength imbalance, that needs professional assessment.
Ready to build a workout program that actually works for your body? If you are tired of piecing together conflicting fitness advice from social media, we can help. The Innova Vita Health & Wellness Course offers a complete, step-by-step blueprint for beginners. Our comprehensive Exercise Programming module will teach you how to safely build resistance and cardio routines tailored to your unique anatomy, complete with AI-assisted tools to help you customize your workouts.
