What are knee and leg casts?

Knee and leg casts are rigid covers that keep your knee and lower leg still. Your doctor uses this treatment when you break a bone or injure a joint. The cast holds the bones in proper alignment and doesn't allow them to move. This helps them heal properly.

Casts are most often made out of plaster or fiberglass material. These form a hard covering on the outside. There are layers of padding for cushion and comfort on the inside.

What to expect from knee and leg casts

Your doctor will do x-rays and take pictures of the inside of your body before you get a cast. This helps them confirm the broken bone and its location. The doctor may need to set or realign the break and get the bone back into its proper position. They can often do this with their hands. In complicated breaks, they might need to realign the bone with surgery.

First, your doctor puts a stocking over your knee and leg where the cast sits. Next, they roll layers of cotton padding over the stocking as a cushion. This can also apply slight pressure to the bone to help it heal. Finally, the doctor rolls on wet casting material on top. The cast starts to harden in the first 10 to 15 minutes. It may be fragile for the first one to two days until the casting material hardens.

In the first few days after the injury, it's important to keep your leg elevated. This reduces pain and swelling. It's also important to keep the cast dry the entire time you wear it.

Avoid swimming and doing other water activities. Covering and sealing it in plastic can keep the cast dry while you bathe.

The amount of time you have to wear the cast depends on your injury. Broken bones take several weeks to several months to heal completely. Your doctor may give you crutches to help you move around without putting weight on your leg.

Be sure to alert your doctor to any discomfort with your cast, especially pain, tingling or numbness in your toes. These symptoms may mean there's too much pressure or swelling in your leg.

Common conditions requiring knee and leg casts

Doctors use casts any time it's important to keep your leg or knee completely still. While people usually get casts because they have broken bones, other conditions that may require knee and leg casts are:

  • Severe sprains
  • Recovery from surgery
  • Damaged tendons or ligaments, which are strong tissues that hold together your joints, bones and muscles

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