What is a broken knee?
The bones of the knee joint are the upper leg bone (femur), the lower leg bones (tibia and fibula), and the kneecap. When one of the bones that make up the knee joint is broken or cracked, it is called a broken knee or a knee fracture. These bones are usually injured from a direct blow to the knee or from a twisting injury. Occasionally the injured bones are also out of alignment with the other bones in the joint. This is called a dislocation.
A child's bones are different than adults in some important ways. First, the bones of a child are more flexible. Sometimes the bones crack like green branches from a live tree instead of snapping like a dry stick. Other times the bones just buckle slightly. When this happens, the bone is broken but there isn't a clear fracture line just a slightly raised area on the outside of the bone. The second major difference is that a child's bones are still growing. Bones grow from an area near their ends called the growth plate. Sometimes fractures occur within the growth plate and can be difficult to see on an X-ray. Fractures in this area can affect the growth of the bone and may require special X-rays or other tests.
What are the symptoms?
Symptoms may include:
- severe pain
- inability to put weight on the leg
- trouble bending the knee
- a grating feeling when the injured leg is moved and the broken bones grind against each other
- muscle spasms
- an obvious deformity of the knee.
How is it diagnosed?
After talking to you and your child about the injury, your child's healthcare provider will examine the knee. An X-ray is taken to see if the knee is broken or dislocated.
How is it treated?
Usually when a bone is broken there is a lot of swelling. If a cast is put on while the knee is still swelling it may cause problems with blood flow to the leg. For that reason the leg is usually splinted for the first couple of days and then a cast is put on. Other times a cast is put on and then the sides of the cast are cut to allow the knee to expand.
The treatment depends on the severity of the injury. If there is only a crack in the bone, a cast to protect the bone while it heals may be the only treatment needed. Other times the bones need to be realigned by pulling and pushing them back into place. If this is necessary, your child will be given strong pain medicine before the bones are moved.
If your child's knee is badly broken or if the bones can't be held in good alignment with a cast, surgery may be necessary. Wires, pins, screws, metal plates and rods may be needed to hold the bones together. The blood vessels around the knee may be injured along with the bones. Sometimes special tests are done to make sure that there is no serious injury to those vessels.
Your child may need to use crutches for several weeks.
How can I help take care of my child?
To reduce swelling, keep the injured knee elevated on pillows when your child is resting. Also, for the first few days it helps to put ice packs on top of the cast for 20 to 30 minutes every 3 or 4 hours.
Most casting material is not made to get wet. If your child needs a cast that can get wet, talk to your provider about special water-friendly.
Don't let your child scratch around or poke things under the cast as this may lead to an infection.
How long will the effects last?
Children tend to heal faster than adults but healing time depends on the child and the severity of the injury. As a general rule most fractures in children heal in 4 to 6 weeks. Your provider may repeat X-rays to check on the pace of healing 2 or 3 weeks after the injury. If the bones are healing well your child may be able to put weight on the leg after a few weeks.
After the cast is removed, your child may need to do rehabilitation exercises. Most of the time pre-teen children are so active that they regain strength and flexibility without physical therapy.
When should I call my child's healthcare provider?
Call immediately if:
- Your child has increased pain, redness, warmth, or swelling.
- Your child has a loss of sensation in the knee, leg, or foot.
- The leg below the cast looks pale, blue, or feels cold.
Written by Tom Richards, MD.
Published by RelayHealth.
Last modified: 2011-01-30
Last reviewed: 2009-12-28
This content is reviewed periodically and is subject to change as new health information becomes
available. The information is intended to inform and educate and is not a replacement for medical
evaluation, advice, diagnosis or treatment by a health care professional.