Quite a number of problems can arise when squatting beneath a heavy load, with one of such problems being the all-too-common issue of a lifter’s knees caving inwards as they go through the range of motion.
This issue in form is otherwise known as knee valgus, and can indicate a number of factors relating to the lifter’s execution of the squat or their physiology itself.
The knees caving in during the squat usually indicates overloaded hip flexors, or otherwise a poor stance width as the legs are placed in a disadvantageous and unstable position - requiring them to shift inwards in order to maintain their range of motion.
The term knee valgus refers to the knees caving inwards, with this occurrence during the squats being considered quite dangerous and can eventually result in chronic injuries of the patellar tendons and surrounding tissues.
During the squat, the knees are meant to remain pointing outwards throughout the ascending and descending portions of the movement - producing a more stable base and ensuring that the hip flexors are capable of functioning within their range of action.
Though knee valgus is usually caused by a previous injury or a muscular issue, poor mobility can also rarely be a factor and is the most likely culprit if muscular weakness or shortened tendons have already been eliminated.
Knee valgus is a common error during squatting that is nonetheless quite dangerous to leave unchecked, as it can easily result in connective tissue injury and severe chronic knee pain.
Knee valgus can also be an indicator of several other physiological issues relating to muscular weakness, muscular imbalances or general poor mobility that can otherwise result in injuries not normally associated with the knees caving in when under load.
In rare instances, knee valgus can even result in permanent damage to ligaments along the legs and lower torso, permanently altering the lifter’s range of motion and maximum force output unless rehabilitative surgery is performed.
If you notice even a slight caving of your knees during squatting, it is best to stop performing working weight sets until an appropriate measure has been taken to prevent further knee valgus.
Apart from more obvious reasons like a history of injury or poor footwear, there are several causes of knee valgus that have to do with issues in the physiology of the lifter, or in the lifting techniques they employ while performing the squat exercise.
The first and most easily remedied cause of knee valgus is simply that the exerciser does not notice when their legs have begun to cave inwards - an occurrence that is especially common among novice lifters who have yet to build the unconscious muscle memory of maintaining outward-facing knees while squatting.
Performing squats in front of a mirror or with the supervision of a more experienced weightlifter can easily and immediately remedy this particular issue.
Another reason why the knees may cave in during the ascending phase of the squat is poor ankle mobility, wherein the lifter will angle their lower leg inwards so as to compensate for their rigid ankle joint, pointing the knees inward and resulting in a host of other issues with the squat.
While this can indeed be caused by an excessively wide stance or poorly suited footwear, it is entirely possible for an individual to simply have poor ankle joint mobility that results in pronation of the foot.
To remedy this issue, simply performing a mobility drill that involves the ankles should be sufficient - or, purchasing special athletic footwear specifically made for the squat.
Having poor hip adductor and abductor muscles can cause a lack of femur stabilization to occur, which in turn translates to the knees caving in somewhat as the quadriceps are forced to compensate for this lack of accessory muscle support.
Unlike other causes of the knees caving in during squats however, having weak hip flexors is somewhat more difficult to remedy on account of the muscles being nearly impossible to isolate in training - meaning that the surest way to fix such an issue is to deload your squat instead.
In particular, having underdeveloped or unbalanced gluteus medius muscles can result in poor adductive rotation of the legs, causing them to be unstable or to otherwise entirely collapse inwards when placed under excessive load.
This specific issue requires rehabilitative or strengthening exercises that directly target the gluteal muscle group as a whole, and can likely cause further problems if left unchecked for long periods of time.
One possible reason why the exerciser’s knees cave in during the squat is simply because of their stance - in the event that they have placed their feet too far apart or facing too far outwards, the disadvantageous position can force the foot to pronate or otherwise roll inwards, drawing the knees together as well.
In most cases, squatting with the feet set slightly wider than hip width apart is the ideal stance - and if a wide stance is the reason why the knees are found to be caving inwards, then adjusting the foot width will immediately rectify the problem.
Attempting a one repetition maximum or otherwise overloading the muscles of the lower body can cause failures in isometric contraction, resulting in the knees caving inwards as the muscles struggle to maintain their stability.
This is entirely normal if you are indeed attempting a maximum squat load repetition - but is something to pay attention to if it is occurring during a working weight set. If so, it is best to reduce the weight of your squat as it is likely too heavy.
A large majority of knee valgus cases are caused by weakened hip flexor or gluteus muscles, either from living a sedentary lifestyle or improperly executing compound leg exercises over multiple training sessions.
While this is seemingly a small problem, it can easily lead to chronic conditions and injury over time, and is rectified by performing rehabilitative exercises to combat the specific weaknesses that the lifter may have.
In the case of a unilateral muscular imbalance, performing one-sided exercises that force each muscle to work independently of the other is the surest way to aid such an issue.
Otherwise, if the muscle group is simply weakened, performing isolation exercises that target the area such as barbell hip thrusts or leg curl machine exercises are quite effective.
If a muscular imbalance or weakness is not to blame for your knees caving in during the squat, its possible that poor mobility is the culprit.
There are two areas known to directly cause knee valgus due to poor mobility; the ankles, wherein the feet will pronate, and the hip flexors wherein ascending during the squat can push them outside of their stable range of motion if not properly stretched.
Poor mobility can come as a result of a sedentary lifestyle, as a side-effect of previous injuries or simply from the natural course of age - meaning that without a consistent and effective mobility routine, it is likely that you will develop poor mobility over time.
In order to remedy knee valgus caused by poor joint mobility, it is important to first identify the problem area prior to performing mobility exercises that target said area.
For the ankles, performing a runner’s stretch alongside toe points on a regular basis should be sufficient enough to remedy pronation under load.
Otherwise, for the hips, exercisers may wish to perform deep squat holds and kneeling hip flexor stretches, as these are the largest range of motion stretches for the hip muscles.
Finally, if there is no physiological issue with the lifter themselves, it is likely that their actual performance of the squat itself is the problem.
As was previously mentioned; having an improper stance, utilizing too much weight or otherwise simply not being aware of your own knee position can all lead to knee valgus despite there being no actual problems with your legs.
Correcting this specific cause of knee valgus is rather complicated, as there are quite a number of reasons and factors as to why the lifter may be performing their squat incorrectly. In certain cases, it is even possible for a lifter to mistake improper squat execution for muscular weakness or poor mobility.
The surest way to remedy this issue is to consult an athletic coach who can assess your form so as to make adjustments as needed.
Otherwise, keeping the foot stance at less than shoulder width, moving the hips and knees simultaneously, keeping the head pointing forward and the core muscles tight are all important cues that lifters should follow in order to avoid knee caving as much as possible.
Yes - knee valgus refers to the knee caving inwards during movement, regardless of whether it is a squat or a jump.
Knee valgus can even occur during ordinary walking or climbing up a staircase, leading to high levels of stress being placed on the various structures of the legs.
Knee valgus is a serious physiological condition that must be rectified as soon as possible if experienced frequently, as quite a number of different injuries may be sustained if the condition is left unchecked.
In the majority of cases, knee valgus is not permanent and is even capable of resolving on its own.
However, the usage of physical therapy methods like strengthening resistance exercises and mobility drills will nonetheless accelerate the recovery from this condition, and can otherwise prevent it in the case of individuals that are predisposed to developing it.
It should be noted that there are indeed cases of permanent knee valgus, of which usually have to do with permanent injuries that have altered the form and function of an individual’s legs and are otherwise outside the capabilities of ordinary physical rehabilitation.
In the case of squats, it is likely that knee valgus will indeed continue to occur unless the particular cause has been rectified.
Now that we’ve covered the why and how of your knees caving in squats, it’s time to implement the right procedures. Identify the cause and devise a plan on how to fix it.
If you’re unsure of how to go about doing this, seeking the advice of a professional should make things both simple and comfortable.
And remember, a small amount of knee valgus during particularly heavy squat sets is entirely normal - it is when the knees begin to cave in on a regular basis during working weight sets that it can become an issue.
1. Rinaldi, V.G., Prill, R.S., Jahnke, S. et al. The influence of gluteal muscle strength deficits on dynamic knee valgus: a scoping review. J EXP ORTO P 9, 81 (2022). https://doi.org/10.1186/s40634-022-00513-8
2. 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 Nov 6;17(21):8208. doi: 10.3390/ijerph17218208. PMID: 33172101; PMCID: PMC7664395.
3. Padua, D. A., Bell, D. R., & Clark, M. A. (2012). Neuro muscular Characteristics of Individuals Displaying Excessive Medial Knee Displacement. Journal of Athletic Training,47(5), 525-536