As a Sports Physiotherapist who’s worked with elite runners and athletes, I believe that the Quadriceps are the key to preventing excessive knee valgus, or ‘knee’s caving in’ during athletic performance.

That’s not to say that we can forget about the glutes, but rather, not to overlook the quads because we’re flooded with social media posts pushing strong glutes as the fix to all knee issues. 

I think strong quadriceps should be the first line of action to combat ‘knees caving in’, or ‘valgus’...and more importantly, to prevent knee injuries. 

Especially so when it comes to the athletic population who are involved in running and change of direction manoeuvres at high velocities (speed). 

CURRENT, MAINSTREAM THOUGHT PROCESS

Look at any instagram page of Physios/rehab trainers/coaches and they’ll more than likely tell you that you need ‘stronger glutes’ to prevent knees caving in, which then prevents injuries like ACL tears or Patellofemoral Joint Pain (knee cap). 

‘Using more glutes’ is synonymous with using a ‘hip strategy’. More on that later. 

Once you get the glutes ‘activating’ better it brings your caved knees into more of a straightened position and then the problem is solved! 

Right?

THE MORE LIKELY CULPRIT (I.M.H.O)

One issue with this is that the mainstream thought process views weak glutes & knee valgus as the ‘cause’ of knee injuries, where, in my opinion (and other biomechanists) … it’s just a symptom of lower limb insufficiencies. 

In plain english - getting someone to stick their knee out so their leg looks straight when they’re exercising is just covering up a fundamental, underlying issue. 

And that issue is a weak quadricep muscle.

Even more specifically, weak inner range quads. 

THE ISSUE WITH AN OVER-RELIANCE ON A HIP STRATEGY?

Here’s where it starts to get a bit technical/geeky - stay with me. 

Let’s take a look at the most notorious knee injury - an Anterior Cruciate Ligament (ACL) rupture. It is MOST VULNERABLE at about 20-30 degrees of knee flexion + some twisting on the knee, and usually at high speeds. 

That means most ACL injuries happen when someone is running at speed, or landing from a jump, then plants their foot down with a bit of knee bend and twists in that ‘caved in’ or ‘valgus’ position. 

The below photo demonstrates someone (me lol) landing with a hip strategy. 

Peep the knee angle I’m in (it’s 20-30 degrees = ACL vulnerable).  

So even though from the front it may look like my legs are pretty straight, and not caved in, my knee is in a vulnerable position. And if I were on the football pitch, I’m probably going to be trying to change directions. 

In fact, the hip strategy may seem fine in a gym or rehab setting when you aren’t in a high speed situation.

But in reality, when decelerating from high speeds, this strategy will create compensations into your pelvis and trunk, that will end up forcing your knee into a valgus position.

Biomechanically,  landing/decelerating/changing direction at a high speed with a hip strategy will cause the contralateral pelvis to drop/rotate, and the forward trunk lean and rotation will naturally create a massive valgus force in the knee. 

Equals poorer performance and higher chance of injury. 

WHAT SHOULD ACTUALLY HAPPEN IN REAL LIFE

If we take a slow motion video of a healthy athlete who’s running at speed and needs to decelerate immediately, they are able to keep their torso relatively upright, their knees bend to absorb load, maybe even translates forwards too, and all this action at the knee is controlled almost exclusively by the quadriceps muscles. 

When you have strong quads, working hand in hand with your glutes, then you have a body that is able to control your lower limb optimally! 

Your Quads are able to control your shin angle and absorb force by bending the knee (knee flexion), while your glutes are able to maintain good hip, pelvic and trunk control. 

Basically - having strong quadriceps muscles reduces the compensations further up the chain in the hip and pelvis that end up creating the knee valgus in a high speed situation! 

CONCLUSION

Just to clarify - I’m not bashing glute exercises at all. They’re a crucial part of a healthy body! 

It’s just that in the athletic population, ESPECIALLY those coming back from a knee injury or surgery, you will need even more quad strength than you think. 

Give the knee extension machine some love, get the quads firing hard, train knee dominant squat patterns, lunge patterns, step up/down patterns…and you’ll be on your way to better athletic performance and reduced risk of knee injuries.

If you’re unsure on where to start, reach out to us! We want to hear what you’re struggling with, and we’ll send you some resources to help get you started to a healthier, stronger knee!

About the Author 

Ryan Tan is our Clinical Director and Physiotherapist here at Physiologic Hong Kong. He’s had over 10 years of experience as a sports and musculoskeletal Physiotherapist, having looked after elite athletes such as the NZ Rugby 7’s team and more recently, some of Hong Kong’s top Trail Runners. His post graduate training in Advanced Lower Limb Rehabilitation alongside his Strength and Conditioning qualifications blends clinical expertise with exercise prescription to provide the best recovery journey for his clients, every step of the way.