It also makes them last longer.

Your doctor will make sure that all the pieces of your broken bone are in their proper places. Then he'll put on the cast to prevent the pieces from moving while they heal. This way they'll grow back together into one bone. It also prevents injury to the area around the bone. Most kids with broken bones say it actually feels much better once the cast is on.

How long do you have to wear a cast? Sometimes it's only for a few weeks. Sometimes it's much longer. It depends on the type of injury you have.