Let’s talk clamshells & why they help your knees.
What? Aren’t they the most ridiculous, outdated exercise ever? Useless as a movement tool and relegated to the days of Jane Fonda and leotards?
I say no!
I actually love clamshells, but only when they’re done mindfully and as part of a whole body approach to movement. Targeting your deep hip muscles is a terrific support for your hip joints, keeping your torso still gently works your core and the strength you build in your hip muscles helps to re-align your knees.
But the usual cuing of “lift your knee” doesn’t generally target the deep hip rotators, and that misses the beauty of a good clamshell.
Here are most of the muscles involved in external rotation (we’ll deal with sartorius another day!).

Why is this important? And how does it affect my knees?
How your legs are placed, supported and moved from your hip joints by all those deep little muscles is crucial for hip health and knee positioning. Your feet also affect your knees and you can read about that here.
If your knees tend to track in towards centre when you move through the world, then changing them needs to start from either end. Trying to change it while you’re actually doing something (walking, running, jumping, squatting, etc) is really complicated and maybe not possible. If your feet are on the ground, then the whole foot-shin-knee-thigh-hip chain is dictated by the need for your foot to meld to the unyielding surface.
And here’s where the humble clamshell shines!
When you lie on your side, with your feet not required to meet the ground, you remove a limiting condition. When you bend your knees, you shorten the lever of your leg and thus lessen the load for your hip muscles. That makes it an easier place for your tissues to do the work and your brain to connect to what might be an unfamiliar motion.
Doing a set of focused, finicky, mindful clamshells BEFORE you head out and do your bigger, more fun and functional thing is a fantastic way to introduce a motor skill, activate support, wake up your brain and prepare to load your muscles, joints and other tissues to serve you for awesome, lifelong, resilient, durable, sustainable, lifelong health and wellness. And isn’t that what we all want?
I know I do!
Look at how much I changed the position of my leg and knee in one short, targeted session!
The left pictures show how when I orient my feet forward, my knee pits are so internally rotated that you can only see one of the two connecting ligaments that should be facing straight back.
On the right, can you see how different my left leg looks? It’s aligned more to centre, so when I move around, my knee is better settled between my thigh and my shin and won’t get strained or stressed unnecessarily.

Yay! Clamshells for the win!
Are you in?
Try this short tutorial for how to make the most of your clamshells and see if you get the same kind of outcome I did!
Want a more detailed how-to? Try this one for a standing half-clam as well as a sneaky trick to avoid tipping your pelvis back!

Alison Crouch
I’m the owner of Boomerang Pilates and creator of the Move SMART program. I teach teachers how to incorporate sustainable movement and authentic teaching in their classes.