Understanding Knee Valgus

Traditionally, knee valgus (knee cave, knock knees) has always been seen as a dangerous movement that is detrimental and should be avoided at all costs. You could walk into almost any gym and you will always hear the common cue “KNEES OUT” being thrown around always. However, before we demonize this movement, we have to really understand what the movement actually is and why people may think that it is a dangerous issue.

We often see this movement commonly occur in two different categories with the first category of team sports such as basketball, soccer, football and the second category with weightlifting sports (Crossfit, Powerlifting, Olympic Weightlifting) involving squatting patterns. While they are both valgus movements, they are both very distinctly different variations of valgus.

Knee Valgus Definition

Knee Valgus is a combination of movements that occur at the hips, knees, and ankles which result in the knees coming in towards the midline of the body

Category 1: Knee Valgus in Dynamic Team Sports

Taking a look at dynamic team sports, we see athletes demonstrate some form of knee valgus – typically during cutting, running, or decelerating and landing after jumping. From the literature and current research, we know that when jumping and landing on a stiff knee (usually 25-30deg knee flexion) at a high velocity with knee valgus occurring, we significantly increase our risk of injury – especially to the ACL (anterior cruciate ligament) in our knee. (Quatman et. Al 2014). We also see that these forces causing injuries occur within milliseconds (49ms) of contact with the ground and that there isn’t anything the athlete can do to prevent it from happening during game time situations. (Quatman et. AL 2014).

However, knowing that this is a movement that is inevitable during high intense game time situations, there are factors that we can take into considerations to help decrease risk of that injury occurring by preparing our body to tolerate and meet in game demands.

  • Overall load management, sleep, stress, and recovery leading up to games

  • Optimizing overall hip and knee strength to be able to tolerate deceleration and landing forces

  • Controlled training into a valgus position

Category 2: Knee Valgus During Squats

When we see the knees caving in during a heavy squat variation (back squat, front squat, clean, snatch etc) there are many different characteristics that make it different than the one seen with impact landing after jumping seen in dynamic sports where we can say it is a safe movement.

  • Athletes squat well below 25-30deg (the range where the majority of ACL injuries occur with valgus)

  • Valgus is occurring bilaterally on both legs

  • The athlete is not landing after jumping at a high velocity with a sudden forceful change of direction

Additionally, when taking a look at the current literature and research, we see that the majority of knee injuries in elite competetive weightlifters are actually due to a chronic tendinitis overuse issue instead of a sudden forceful traumatic accident consistent with ACL injuries (Calhoon et. al 1999).

Hip Adductors – the real cause of Knee Valgus in Squats

Often times you may hear “your knees are caving in because you have weak hip abductors, and that strengthening your glutes you will fix your knee valgus” However, I think it’s a pretty safe bet to say that the world champion lifters squatting and cleaning well over 400lb-500lb with knee valgus most likely don’t have “weak glutes.”

Rather, research and EMG studies have shown that our hip adductor muscles (the muscles that are responsible for bringing our leg in towards the midline of our body) are actually the MOST ACTIVE muscle during hip extension – the movement occurring as a lifter is coming up from the bottom of a squat position (Benn et. Al 2018), (Vigotsky et. al 2016). This could explain why we see lifters demonstrate this quick valgus coming up from the bottom and then drive back out towards neutral as the glutes take over the majority of the movement around parallel. During max effort lifts with high percentages or with higher reps, our body will recruit every muscle possible in order to complete the movement and so that quick knee valgus moment is simply just a positive adaptation our body has towards training.

Acceptable Valgus Variations During a Squat

  • Occurring only on the bottom concentric portion of the squat (coming up from the bottom)

  • Occurring bilaterally on both lower extremities

  • Should be brief and dynamic

  • Expect to see during higher heavier percentages, high volume with moderate percentages, and not during a body weight squats.

  • Knees should track back out towards neutral as the athlete nears parallel.

Unacceptable Valgus Variations During a Squat that MAY Require Intervening

  • Uncontrolled knee valgus on the descent (eccentric portion of the squat)

  • Unilateral knee valgus only on one side

  • Prolonged and excessive valgus

  • Excessive valgus during a regular body weight squat

There should be a ton of different factors and considerations that go into what is acceptable vs. non-acceptable. Knee valgus during a squat position is more of a gray area and doesn’t necessarily have a black and white answer in terms of what is good or bad but rather falls more along the lines of “it depends” especially on the individual, their training history, and current situation in front of you.

For more information, check out our in depth YouTube video on this topic!