Please Your Knees

Stand strong and avoid injury by learning how to prevent hyperextension of this vulnerable joint.

By Roger Cole

You're balancing confidently in Ardha Chandrasana (Half Moon Pose), and the pose feels firm and steady. There's only one problem: You're hyperextending the knee of your standing leg. When you extend, or straighten, your knee beyond a straight line, it's called hyperextension, which can injure the knee and other parts of your body. It's quite common among yoga students at all levels, and certain asanas can exacerbate the condition if you repeatedly do them incorrectly. Fortunately, you can learn to practice in a way that both aligns and protects your knees and makes them stronger and healthier.

What's my Line?

When a knee that isn't prone to hyper-extension extends, its ligaments—the cords of connective tissue that join the thighbone to the shinbone—pull taut and stop the two bones at the point where they lie directly in line with each other. If your knee hyperextends, that means its ligaments are too long, and so they don't stop the bones until your leg has moved beyond a straight line. If you're uncertain about whether your knees hyperextend, stand sideways in front of a full-length mirror, gently press your knees backward until you are unable to move them back any further, and envision an imaginary line running down the side of your leg from your hip joint to your ankle. If the center of your knee ends up behind that line, it is hyperextended.

Standing with your knees locked back in hyperextension can cause a host of problems in your knees and also in your legs, hips, and spine. In addition to overstretching the ligaments, hyperextension stresses the front of the knee joint surfaces and weakens the quadriceps muscles. Over time, this misalignment may create deeper hyperextension, ligament strains or tears, cartilage degeneration (including meniscus damage), and arthritis of the knee joint or kneecap. What's more, if you push the knee back with enough force, you can tear a ligament, most likely the anterior cruciate. Standing in hyperextension puts excess pressure on your heels and the front of your shins, which can lead to inflammation. It may also tilt the top of your pelvis forward, which can stress your hip joints, overarch your lower back, and disturb your posture all the way up to your neck and head.

Some people develop hyperextended knees at an early age, so the condition may be partly genetic, but it's also likely that posture and movement habits (especially in activities like dance, gymnastics, or yoga) can exacerbate the condition. Even everyday habits can contribute: The soleus, a calf muscle, can pull the shinbone back. Tightness in this muscle—for example, from wearing high heels—might help create or worsen hyperextension.

Some yoga poses, such as Trikonasana (Triangle Pose) and Ardha Chandrasana, tend to strongly push the knees back toward hyperextension if you don't practice them with care. In Trikonasana, the angle of your front leg to the floor invites gravity to push your knee into extension, and as you sidebend over the leg, the weight of your torso magnifies the effect. In Ardha Chandrasana, you put all of your weight on one leg and then straighten it fully, so if your knee is even slightly hyperextended, your body weight will often push it back more. To keep your knees healthy, it's important to learn how to do these and similar poses safely.

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