You step onto the platform ready to squat deep and heavy. But instead of congratulating your Herculean efforts, all your coach and gym buddies can shout at you seems to be “knees out.” On watching the recording they took, you notice that your knees caved in as you started your squat ascent. But is this always and without exception an actual problem? When knee valgus strikes, must you quake in fear?
Knee valgus may sound intimidating and, if you’ve been on the receiving end of the “knees out!” shout, bad for your performance in the gym. But it’s a simple concept on the surface. Knee valgus refers to lateral movement of the knee joint while bending or extending your leg.
Whatever you choose to call it, it’s important to assess what is causing your knees to collapse. It can help to determine whether your degree of knee collapse is dangerous, a sign of muscle weakness, or simply a movement that comes with your individual limb length and body type.
What is Knee Valgus?
Knee valgus is when the knees buckle inward — most often, you’ll see this during a barbell squat. To varying degrees, it may look like a bow being strung and released. Your knees will gravitate toward each other momentarily, then drift apart again as you clear the toughest part of your squat.
Different athletes and coaches have very different opinions about why this happens — and what, if any, degrees of knee valgus is acceptable and safe. Knee valgus is often thought to be connected with knee pain, and several studies suggest that the more your knees collapse, the more knee pain you’re likely to have. (1)(2) Other studies show that some degree of knee valgus is not necessarily dangerous. Rather, it can be a natural result of your biomechanics and limb lengths. (3)(4)
Why Do Your Knees Cave in When You Squat?
As with so many factors in lifting, the reason someone’s knees cave during a squat may vary from person to person, and even attempt to attempt. For example, your limb length might make you predisposed to a small degree of knee valgus during most squat attempts. But when you’re working at a high percentage of your one-rep max, that valgus could possibly become dangerous if it becomes very exaggerated under such intense pressure.
Even if you both have excellent form, your squat probably doesn’t look exactly like your gym buddy’s. That’s because every lifter has different biomechanics, limb lengths, and relationships with movement.
Research suggests that the ratio of your pelvic width to femur length might contribute to knee valgus, which is more related to anatomy and limb length than technique or muscle imbalances. (3) Studies have also found that your plantar arch index — the ratio of your heel width and midfoot width when standing — can impact varying degrees of knee valgus. (4)
These variations aren’t necessarily bad or pain-inducing. Just like lengthy arms mean your bench press grip and angles are a bit different than someone with T-rex arms, different anatomy might just change how your squat looks.
Muscle Imbalances or Weaknesses
Practically speaking, when your knees shift inward, your body is attempting to generate force. Studies have found correlations between ankle mobility and hip, quad, hamstring, core, calf strength and a lifter’s degree of knee valgus. (5)(6)(7)(8)(9) Knee valgus may well be signaling to your body that your muscles and joints need help completing the squat.
When this happens, your knees may well cave inward to allow your adductors to assist with hip extension. If you’ve ever felt groin or knee pain during your squat, this might have happened to you. Your ankles may also be signaling that they’re not mobile enough to support you the way you need during your squat. (7)
Local muscles aren’t the only parts of you that become accustomed to your movement patterns while training and moving in your daily life. Your central nervous system also plays a role in the neural patterning that informs your lifting.
That’s why so many coaches will say that if you want to get better at squatting, you should squat more often — so that your brain can practice good form over and over again. Research suggests that your central nervous system does indeed play a role in creating or averting knee valgus. (11)
Is Knee Valgus Always Bad?
Studies suggest that, sometimes, knee valgus is about the shape of your body rather than muscular weaknesses or mobility inefficiencies. One study identified that people with longer femurs relative to their hip widths are more likely to experience knee valgus. (3) Another study suggested that limb length can directly impact knee valgus in single-leg squats. (4)
It’s important to note that knee valgus’s bad reputation might, in part, come from studies suggesting that landing from a jump with high degrees of knee valgus is associated with higher rates of ACL injuries. (12)
However, one study suggests that higher degrees of knee valgus in single-leg squats is not necessarily predictive of non-contact ACL injuries. (13) In other words, knee valgus — during more stable movement conditions — doesn’t always seem to mean that you’re setting yourself up for a later injury.
Similarly, some clinical trials have shown that specifically strengthening your glutes can reduce pain levels, but that doesn’t necessarily change your movement patterns. (14) Knee valgus may not always cause pain, and strengthening your related muscles can benefit your squat and reduce discomfort without necessarily “fixing” your knee collapse.
How Do You Know if Your Knees are Caving Too Much?
The first thing to check for with any kind of lifting form issue is pain. When your knees cave, does it hurt? If yes, you probably want to check in with an experienced coach or physical therapist familiar with lifting to make sure you don’t have underlying injuries that you can exacerbate by squatting.
Second, check in with yourself about when your knees cave. Does it only happen with heavy weights? The heavier the weight, the more neuromuscular control and coordination your body needs to maintain correct form and avoid knee valgus.
For a lot of lifters, form starts to break down as the weight gets heavier. That may well include weight-induced knee valgus. Typically, try to aim to keep your heavy squats looking pretty similar to your more moderate-weight squats. Keeping consistent form — both physically and mentally — can help you lift more efficiently across the board.
If your knees cave a little bit but they don’t drift inward further than your big toe — and there isn’t pain — it may not be such a big deal. But if as soon as you hit 80 percent of your 1-rep max, your knee pivots inward? You may want to press pause on squatting that heavy until you can correct the issue.
How to Fix Knee Valgus
If you’re experiencing pain from knee valgus, you probably want to address it ASAP. The less sharp pain you experience while you train, the more efficiently you’ll be able to move — and the heavier you’ll be able to lift.
- Ankle (mobilize)
- Midfoot (mobilize)
- Hips (mobilize and strengthen)
- Glutes (strengthen)
- Quads (strengthen)
- Hamstrings (strengthen)
- Calves (strengthen)
- Core (strengthen)
It’s important to evaluate your own movements and needs based on your knowledge of yourself, your training, and where there may be potential gaps in your program. Are squats and deadlifts the only time you’re training your hamstrings? Knee valgus or not, you might want to add some hamstring curls to your repertoire. Neglecting your calves? Bumping weighted calf raises and ankle mobility exercises up in your program can help.
You might also want to pay attention to unilateral moves that will target one leg at a time. This way, you can fight knee valgus while avoiding accidentally reinforcing any strength or muscle imbalances. Below, you can find three different approaches to this type of training to combat knee valgus.
Elevated Pistol Squat
Trying to do a pistol squat without wobbling can be enough to stimulate the glutes, abductors, and other muscles to reduce knee valgus. Because it’s a unilateral move, you’ll be strengthening your muscles from both sides and avoiding promoting strength imbalances.
And, since the move is elevated you don’t need quite as much coordination and control as you do for the full version. But it’s still very challenging and will serve as a solid leg and core workout all its own.
Banded Pistol Squat
To get your neuromuscular training in order, you want to help your body work with your mind to “program” yourself to squat with less valgus. For this, you’ll do a pistol squat with a resistance band pulling your knee inward. The idea is to teach the body what valgus feels like so it can learn to correct it. It allows your body to turn on those glutes on the lateral side of your body and keep your knees stable and in line. You’ll also be working your lateral core.
Another classic way to train with this neuromuscular principle in mind — especially if you can’t do pistol squats — is to do banded squats with a strong mini band around your calves or thighs. Your body will automatically push your knees out by fighting against collapsing under the band’s pressure. Doing exercises like this with enough repetition teaches your body muscle memory about the squat pattern you’re trying to create.
Standing Unilateral Abduction
Consider performing a standing unilateral abduction with a band around the ankle and a small hinge at the hip. But there’s a twist: it looks like a strength exercise for the leg that’s kicking out to the side, but it’s actually a stability exercise for the standing leg.
This move will help activate your calves, glutes, core, and hips — many of the groups you want to target if you’re looking to reduce valgus.
Listen to your body when it comes to assessing your movement patterns. It’s rarely a bad idea to get stronger and more mobile overall. So if you want to reduce knee valgus and any associated risk of pain or injury, by all means, work on ankle mobility and hip, hamstring, glute, and quad strength. This is a recipe for a better overall squat (and athlete) regardless of your angle of knee collapse.
It’s also important to remember that movement deviations are not always intrinsically bad. Instead, it’s all about context — and, sometimes, about your limb length and body type. Excessive valgus that causes acute pain? Address it. Minor, painless knee movement on heavy lifts only? Monitor it and work on your form, but don’t necessarily panic.
- Scholtes SA, Salsich GB. Consistency Of Dynamic Knee Valgus Kinematics And Pain Across Functional Tasks In Females With Patellofemoral Pain: A Cross-Sectional Study. Int J Sports Phys Ther. 2020;15(6):985-994.
- Emamvirdi M, Letafatkar A, Khaleghi Tazji M. The Effect of Valgus Control Instruction Exercises on Pain, Strength, and Functionality in Active Females With Patellofemoral Pain Syndrome. Sports Health. 2019;11(3):223-237.
- Pantano KJ, White SC, Gilchrist LA, Leddy J. Differences in peak knee valgus angles between individuals with high and low Q-angles during a single limb squat. Clin Biomech (Bristol, Avon). 2005 Nov;20(9):966-72.
- Mozafaripour E, Seidi F, Minoonejad H, Mousavi SH, Bayattork M. Can lower extremity anatomical measures and core stability predict dynamic knee valgus in young men? J Bodyw Mov Ther. 2021 Jul;27:358-363.
- Coelho BAL, Rodrigues HLDN, Almeida GPL, João SMA. Immediate Effect of Ankle Mobilization on Range of Motion, Dynamic Knee Valgus, and Knee Pain in Women With Patellofemoral Pain and Ankle Dorsiflexion Restriction: A Randomized Controlled Trial With 48-Hour Follow-Up. J Sport Rehabil. 2021 Dec 29;30(5):697-706.
- Crowell KR, Nokes RD, Cosby NL. Weak Hip Strength Increases Dynamic Knee Valgus in Single-Leg Tasks of Collegiate Female Athletes. J Sport Rehabil. 2021 Jun 20;30(8):1220-1223. doi: 10.1123/jsr.2021-0043.
- Wilczyński B, Zorena K, Ślęzak D. Dynamic Knee Valgus in Single-Leg Movement Tasks. Potentially Modifiable Factors and Exercise Training Options. A Literature Review. Int J Environ Res Public Health. 2020;17(21):8208.
- Macrum, E., Bell, D. R., Boling, M., Lewek, M., & Padua, D. (2012). Effect of Limiting Ankle-Dorsiflexion Range of Motion on Lower Extremity Kinematics and Muscle-Activation Patterns During a Squat, Journal of Sport Rehabilitation, 21(2), 144-150.
- Sahabuddin FNA, Jamaludin NI, Amir NH, Shaharudin S. The effects of hip- and ankle-focused exercise intervention on dynamic knee valgus: a systematic review. PeerJ. 2021 Jul 5;9:e11731.
- Schmidt E, Harris-Hayes M, Salsich GB. Dynamic knee valgus kinematics and their relationship to pain in women with patellofemoral pain compared to women with chronic hip joint pain. J Sport Health Sci. 2019 Sep;8(5):486-493. doi: 10.1016/j.jshs.2017.08.001.
- Llurda-Almuzara L, Pérez-Bellmunt A, López-de-Celis C, Aiguadé R, Seijas R, Casasayas-Cos O, Labata-Lezaun N, Alvarez P. Normative data and correlation between dynamic knee valgus and neuromuscular response among healthy active males: a cross-sectional study. Sci Rep. 2020 Dec 2;10(1):17206.
- Tamura A, Akasaka K, Otsudo T, Shiozawa J, Toda Y, Yamada K. Dynamic knee valgus alignment influences impact attenuation in the lower extremity during the deceleration phase of a single-leg landing. PLoS One. 2017;12(6):e0179810.
- Nilstad A, Petushek E, Mok KM, Bahr R, Krosshaug T. Kiss goodbye to the ‘kissing knees’: no association between frontal plane inward knee motion and risk of future non-contact ACL injury in elite female athletes. Sports Biomech. 2021 Apr 28:1-15.
- Rabelo NDDA, Lucareli PRG. Do hip muscle weakness and dynamic knee valgus matter for the clinical evaluation and decision-making process in patients with patellofemoral pain? Braz J Phys Ther. 2018 Mar-Apr;22(2):105-109.
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