Why "Flex Your Foot to Protect Your Knee" is BS (And What Really Protects Your Joints)

You've probably heard it a gazillion times in yoga class: "Flex your foot to protect your knee."

This cue usually appears when you're in some kind of "figure 4" shape (think pigeon pose, tree pose, or any variation where your knee is bent and your hip is externally rotated.)

But here's the thing: this cue is actually not accurate. And understanding why matters way more than you think.

Let's unpack it.

Joint Protection 101: What Your Yoga Teacher is Missing

In order for a joint to be "protected," a muscle must cross that joint. That's how stabilization works: muscles that span across a joint create tension and support to keep everything in place.

So when we're talking about protecting the knee joint, we need muscles that actually cross the knee. Makes sense, right?

Here's where the common cue falls apart: the muscles that dorsiflex (flex) your foot do NOT cross the knee joint. And if they don't cross the knee joint, they can't really stabilize it.

Let me show you what I mean.

Meet the Dorsiflexors (That Don't Protect Your Knee)

Tibialis Anterior is the primary muscle that dorsiflexes the ankle. It's that big muscle running down the front of your shin. But here's the kicker: it does not cross the knee joint. What it DOES do is stabilize the ankle joint when the foot is dorsiflexed.

Extensor Digitorum Longus also dorsiflexes the ankle. But guess what? It also does not cross the knee joint.

Extensor Hallucis Longus? Same deal. Dorsiflexes the ankle but doesn't cross the knee.

And Fibularis Peroneus Tertius? Also goes nowhere near the knee.

Do you see the issue?

Since the primary dorsiflexors of the ankle do not cross the knee, they cannot create "protection" (stabilization) at the knee. Flexing your foot doesn't protect your knee. It protects your ankle.

So What DOES Protect Your Knee?

Here's what IS true: fascia plays an important role in distributing tension through the body.

When you dorsiflex the ankle, you create what's called global anterior chain tension (a line of tension that runs up the front of your body). This can improve force transmission through a joint, which can be beneficial in certain contexts.

But let's be clear: that's not the same thing as directly stabilizing the knee. It's more about creating a connected chain of tension through your entire leg and body, which can support better alignment and load distribution.

The Bottom Line

"Flex your foot to protect your knee" isn't technically wrong in every situation, but it's definitely not as clear-cut as we've been taught.

The real story is more nuanced: dorsiflexing your ankle stabilizes your ankle, and it can create fascial tension that supports better force transmission. But it's not directly protecting your knee the way the cue implies.

(If you experience knee pain in yoga, check out this article that outlines what to do about it.)

If you’re a yoga teacher, this anatomy knowledge is what takes your yoga teaching to the next level. 

So while it’s absolutely great to cue to FLEX THE FOOT….the REASON for that is not to “PROTECT YOUR KNEE.”

We can flex the foot to stabilize the ankle.
We can flex the foot to wake up the fascial chain on the front of the leg and SUPPORT our joints.
We can flex the foot to increase proprioception and a sense of stability.

Understanding the actual biomechanics helps you make smarter decisions in your practice. Instead of blindly following cues, you can tune into what your body actually needs in each pose.

And that's where the real magic happens.