Let's talk about knees.

Shock absorbers

First of all, ballet dancers rely on their knees for more than they realize. In between the top of the Tibia (shin bone) and the bottom of the Femur (thigh bone), you have two half-moon shaped padded cushion-type-things, called Meniscus. Think of them as shock absorbers. Without them, your bones would be grinding against each other.

But dancers tend to be very hard on their Menisci. We do a lot of jumping, so they do a lot of shock absorbing. But if we don't help them along, they're going to give out.

One of the key ways you can protect your knees is to land your jumps with your knee directly over your two biggest toes, to roll through the foot as you land, and to press your heels into the floor. This distributes your weight correctly and keeps you in alignment, so you don't put extra strain on your knees.

Ligaments

There are tons of ligaments in your knees you need to take care of. The Co-lateral ligaments are two ligaments (that's the "co") on either side of your knees (that's the "lateral"). They keep your Patella (knee cap) from slipping side to side.

You also have the ACL and the PCL. ACL is Anterior Cruciate Ligament (Front, crossed ligament) and the PCL is Posterior Cruciate Ligament (back crossed ligament). They criss-cross under the Patella to keep it from moving forward and back. 

Many athletes tend to injure their ACL. But dancers are at risk of injuring their PCL, mostly because we like to hyperextend our knees, which is very very bad.

See, Ligaments don't stretch back. Once they stretch, they're stuck that way unless you do intense physical therapy or have a surgery. Hyperextension of the knees means you have a loose PCL. If the PCL is very loose, it could tear, strain, or not do it's job (thereby endangering your Patella).

If you are hyperextended, remember not to lock your knees. Your legs should look straight, but that doesn't mean they should be as engaged as they can possibly be! You have to re-train your muscles to stop pushing back, and lift up in your thighs to keep your stability.

Turnout

I will certainly address this topic more fully in another post. But just because this is extremely important, let's mention turnout.

Turnout does not come from your knees.

Turnout comes from your hips.

If you turn out from your knees, you will tear ligaments, rub and tear your Menisci, and cause serious injury to your ankles. (Again, ankles will be another post all together.)

Please, for the love of Marie Taglioni, don't turn out from your knees.