The knee joint is formed by the articulation of the femur (thigh bone) and tibia (shin bone), and also includes the small “cap” of the patella. While the knee does allow for some rotation, the main actions of this hinge joint are flexion and extension. The primary job of the knee is stability rather than mobility as is the case for the ankles and hips.
Knee pain, and instability are fairly common, but the purpose of this brief article is not to diagnose or categorize knee injuries or dysfunction. Certainly if you have a knee injury or pain that is ongoing, we recommend seeking treatment from a doctor or physical therapist. We hope here to provide a basic awareness about how the knee moves, and some ideas for how to keep your knees happy and healthy doing basic daily movements and common exercises.
One of the most important things to look for when exercising or performing daily activities is “joint stacking”. Once you become aware of this idea, you can look for it in just about any exercise or movement you do! Especially if you have some discomfort, pause, and see if you can become aware of your joint stacking. Let’s take a look at joint stacking in a couple different areas:
Squats and Hinges - Letting the knees collapse inward in your squats and hinges can cause knee pain and dysfunction. Make sure you are prying out from the hips and stacking your knees over your ankles and feet. Letting the knees come in front of the toes in your squats isn’t wrong necessarily - in fact, healthy knees and ankles should allow for this movement. But if you have a knee injury or experience pain when your knees reach past your toes, a simple thing you can try is keeping your knees over the ankles and see if that feels more comfortable for you. Also typically when you are under an additional load and lifting weight in these exercises, joint stacking makes the lift safer and stronger.
Asymmetrical/Single Leg Stance and Stepping - Here we get to take joint stacking to the next level and look for more than just the ankle and knee stacking. In split squats, lunges and stepping activities for example, we want the ankle and knee stacked on the front leg, and on the back leg we want the knee, hip, shoulders and head all stacked. Sometimes joint stacking goes awry if we don’t take a long enough stride, if we lean forward rather than staying upright, or if we have the back leg rotated such that the knee bends out to the side. In lateral lunges and squats it’s important to be aware of stacking not just the working knee over the ankle, but making sure you keep the unloaded leg straight so as to not put too much pressure on that knee.
You may need to decrease the range of motion of the exercises mentioned above if you have difficulty performing them with the appropriate alignment. Because the health and functioning of our knees is affected by how our hips and ankles function above and below the knee joint, here are a few of our favorites exercises that work the ankles and hips and are of particular benefit to the knees:
Ankle Mobility/Knee Flexion Drills - yes, these purposefully break our ankle and knee “joint stacking” rule. As we already mentioned, healthy knees and ankles should allow for this movement. And in the case of the exercises below, we are not placing additional load on the body by lifting weights as we would be in squats and deadlifts. These exercises start from easier with the Foot on Bench Drill, medium with Unchair, and challenging with the Foot on Block Reach. Ease your way into these and don’t push to the point of pain. In all of these exercises, see if you can connect to hamstrings (back of your thighs) bending the knee, quadriceps (front of your thighs) straightening the knee, and the muscles up the front of your shin dorsiflexing your ankle (pulling the ankle and toes toward your knee).
Foot on Bench Drill - Stand on one leg with the opposite foot on a bench or box. For the leg on the box, gently bend your knee as far past your toes as you can, while keeping your heel down. Think of activating the hamstrings to bend your knee and the quads to straighten it out again.
Unchair - Stand with your feet together and brace your core to lock your spine into neutral so that it cannot arch or round. We call this move “unchair” because unlike chair pose in yoga where you try to maintain joint stacking of the knee and ankle and sit the hips back into a “chair," unchair asks you to bend your knees past your toes.
Foot on Block Reach - Stand with one foot on a yoga block and find the core bracing you had in unchair. Bend the knee of the leg on the block, and gradually reach the opposite foot further and further forward on the ground in front of you to encourage more forward movement of the working knee.
Knee Extension Drills focus on strengthening and developing your awareness of using the quadriceps to straighten (extend) your knee. We’ve got a simple band drill, and a more challenging step up variation for you:
Seated Knee Extension with Band - While seated with a band around one foot, hold the band in your hands and use it to help you bend your knee as much possible. Then engage the quads against the resistance of the band to fully extend the knee.
Peterson Step Up - Stand with one foot on a box, toes turned out to the side about 10-15 degrees, and the heel lifted as high as you can. The heel of foot on the ground should be lined up with the toes of the foot on the box. Try to lift the toes up on the foot on the ground so that you don’t step with this foot. Instead, engage the quads to straighten the knee of the leg on the box, as you drive that heel down into the box and come into a tall lock out (the opposite foot will have lifted off the floor). Start with a fairly low box, and bodyweight only at first. You can go higher and add weight to these as you progress.
Combined knee flexion/extension drills:
Hamstring Curl - This version uses slides, but you could also use a stability ball or a TRX. On your back with your feet planted in line with the hips, squeeze your glutes to bridge your hips up. Straighten your legs, and then use your hamstrings to bend the knees without letting the hips drop.
Warrior 3 Squats - Stand with your feet together, brace your core and hinge your hips back as in Chair pose from yoga. Fold over until your shoulders and your hips are in line and then take one foot up off the floor, keeping the knees squeezing together. Straighten and bend the standing knee, while staying in the hinged position.
Bonus ideas for knee safety -
Padding under the knee - whenever you are kneeling on a hard surface, place a pad under your knees. This isn’t the time to tough it out, and even if you don’t feel any pain, there is nothing about kneeling on a hard floor that will make your knee stronger over time.
Padding between calf and hamstrings - If postures like Child’s Pose or a standing quad stretch feel painful, try placing a blanket or towel between your calf and hamstring.
Ankle Dorsiflexion - Protect your knee by dorsiflexing your ankle to activate muscles in your shin to stabilize the knee in hip stretches like 90/90 or Thread the Needle.