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As lifters, we constantly strive to perfect our form and improve our strength. Yet, one common issue I see very often as a gym-based physical therapist is a phenomenon known as "knee cave," where the knees collapse inward during exercises like squats and lunges.
While there are several potential causes for knee cave, the most common culprit is a lack of glute engagement.
There is also this belief that some degree of knee cave is OK, as you look at some of the top lifters in the world and even they have it when squatting heavy. While I agree and fully understand that your form at a top set is never perfect, I do not think we should use this argument to completely ignore it, as I've seen time and time again that sleepy glutes are very much a common cause to many back and knee issues.
The Role of the Glutes
There are plenty of muscles in the back of your hip. There are the main glute muscle (gluteus maximus), and smaller glute muscles underneath and more on the side (gluteus medius and minimus). There's also several smaller hip rotators, the most famous one known as the piriformis. When these muscles are weak or not properly engaged, your knees will collapse inward. This can cause more strain on the knees, and cause you to lift with more of your back if the most powerful muscle in the body (glutes) are not helping you as much as they should.
Furthermore, the glutes help keep the pelvis in a neutral position. The glutes work to posteriorly tilt the pelvis, or prevent you from going into an anterior pelvic tilt (arched low back). Many people squat with an excessive arch which can be from poor glute activation. This can cause low back injuries as well.
Addressing Knee Cave: Engaging the Glutes
Before you can start learning to engage the glutes during exercises like squats, it's best to start with some simple basic movements. They may look easy, but they may surprise you if you have weakness here.
Exercises to "wake" your glutes up & begin light strengthening:
Side-lying hip abduction
I made a whole instructional video on how to do this exercise as it is so commonly done ineffectively. Watch below.
How to perform:
Lie on your side with your bottom knee bent and top leg straight.
Ensure your pelvis is stacked and not rolled back.
Engage your core the whole time.
Lift your top leg out to the side, but also a bit back. You should feel it working in your glutes, not in the front of the thigh or hip.
Lower it back down slowly.
Perform 2 sets of 12 reps on each side
2. Clamshells
How to perform:
Place a band around your thighs, just above your knees.
Lie on your side with your knees bent
Engage your core
Open your knees while squeezing your glutes. Keep your ankles together. Slowly lower it back down
You should feel it working the glutes.
Perform 2 sets of 12 reps on each side.
Incorporating Bands into Common Exercises
Now that we've activated the glutes, let's work on finding them during exercises that you're probably already doing. Using a band can not only help to strengthen the glute muscles, but also help teach you how to turn them on properly.
Squats
I'd start out bodyweight and then progressively add more weight if you're able.
Place a band around your legs, right below the knees.
Before you even descend into the squat, engage your core and glutes. You'll notice the band wants to push your knees inward, so you have to do the opposite and push them out. This pushing out movement is the same movement as the clamshell and should come from the glutes (this is why I like to start with the clamshell).
Keep the knees out the entire time. Your knees should be in line with your toes. If they are too far in, you may not be engaging your glutes enough. If they are too far out, you're overdoing it.
2. Lunges
This one requires a bit more of a set-up as you have to perform next to a squat rack pole or something you can attach a band to.
How to perform:
Tie a band around a pole, set to the height of your knee.
Place your outside leg into the band and place it just below your knee. Your other leg should be behind the band.
Perform a reverse lunge. With the band pulling your front knee inward, you must engage your glutes (and core, always) to keep your knee in line with your toe. Feel your glute contracted to slowly lower you down, and squeeze it even more on the way back up.
3. Single Leg RDL
This is an exercise that requires a lot of balance, so if you struggle with that, keep the toes of your back leg planted on the ground for support. This is also an easy exercise to breeze through, but if you've never truly kept the tension on your glutes/hamstrings, be prepared to feel the burn!
How to perform:
Tie a band around a pole, set to the height of your knee.
Place your outside leg into the band and place it just below your knee. Your other leg should be behind the band.
Engage the core and glutes, and then hinge at the hips.
Only go as far down as your hamstring flexibility will allow. Once you feel that point, come back up. Squeeze the glutes even more on the way up.
If you're using a weight, hold one dumbbell in the hand opposite of the stance leg (this increases glute activation).
Conclusion
Knee cave can be a hindrance to your lifting progress by decreasing your muscle gains. In addition, it can also increase the chance of injury to your low back, hip and knee. By understanding the importance of glute engagement and incorporating specific exercises to strengthen these muscles, you may be able to correct your lifting form and minimize injury risk. Consistency is key so practice these movements 2x/week to see the best results.
As a Doctor of Physical Therapy who works out of a gym specializing in powerlifters and bodybuilders, I'm here to help you optimize your performance and stay injury-free, but also deal with those injuries when they come. If you are dealing with an injury or maybe are unsure about your technique and wish to remain injury free, please contact me to schedule an in-person session. I'd love to help! Check out my website to learn more about how and why I specialize in treating lifters.
DISCLAIMER: The content provided in this article is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health care professional. Never delay seeking professional medical advice because of something you have read or seen online. As a physical therapist, I strive to share accurate and evidence based information, but individual health conditions vary and what may be good advice to one person may not work for another and it is unknown unless a full examination is done. Stronger Performance Physical Therapy LLC and Dr. Sarah J Barbosa assume no responsibility for any injuries or health issues that may result from following the advice or exercises demonstrated in this article. If you experience any discomfort or pain during exercises, stop immediately and consult your healthcare provider. By reading this article, you acknowledge and agree to the terms of this medical disclaimer. If you have specific medical concerns or questions, please consult your qualified health care professional.
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