What Is Knee Dislocation?

If you dislocate your knee, that means that the bones that come together at that joint have been thrust out of place with great force. It’s an emergency, and it's very painful.

Dislocated knees are rare, but they're severe. Other parts of your knee might also have been damaged at the same time. You need to see a doctor right away in order to get back on the road to recovery.

Causes

Knee dislocation is usually the result of:

  • Car accidents. If you bang your knee against a hard surface like your dashboard, the force of the blow may be strong enough to dislocate your knee.
  • Sports injuries. This is less common than car accidents, but it’s possible to dislocate your knee if you collide with great force with another player or with the ground when your knee is bent, or if you over-extend your knee (bend it backwards farther than it’s supposed to go).
  • Hard falls. It may happen to skiers or runners who lose control and fall on a bent or overextended knee. You may even dislocate your knee if you fall after stepping into a hole in the ground by mistake.

Symptoms

When you dislocate your knee, you may hear a popping sound. The following symptoms also are common:

  • It hurts a lot. Your knee is in so much pain that you can’t move it.
  • It’s swollen and severely bruised.
  • Parts of the knee look like they’ve been knocked out of place.

How Is It Diagnosed?

You should go to your doctor at once so she can see your knee from many angles to confirm the injury.

Examination. Your doctor will look at your knee, and she’ll want to hear how you injured it. She’ll note whether or not your knee is misshapen and swollen and whether or not you can move it.

Your doctor may push on different parts of your leg to see if you’ve also damaged any ligaments, which are bands of tissue that help to hold the knee in place. It’s common to tear ligaments when you dislocate your knee.

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She’ll also note what your skin looks and feels like below your knee, all the way to your foot. Dislocating your knee may cause damage to nerves or blood vessels, which may change the color and temperature of your skin. This could affect blood flow or your sense of touch below the knee. In extreme cases, you could lose your limb (amputation) if these severe complications aren’t addressed.

Imaging. Your doctor likely will want to see what’s going on inside your knee.

An X-ray can confirm that your bone has been knocked out of the joint. It can also show if there are broken bones from your accident.

An MRI can show whether any of the ligaments or other soft tissues in the knee have been damaged. It can also help a surgeon prepare to rebuild your knee.

Do I Need Surgery?

Your treatment will depend on how badly you’ve been injured.

No-surgery option. If the damage to your knee isn’t too severe, your doctor may try to pop your bone back into place by pressing and moving your leg in certain ways. This will be very painful, probably. Your doctor will offer to give you medicine so that you won’t feel what’s happening. After your bone is back in the joint, you’ll likely need to wear a splint for a few weeks to allow your knee to heal without moving or bearing any weight.

Surgery. Your doctor may need to do surgery to correct the dislocation and other damage from your injury, including:

  • Broken bones
  • Torn ligaments
  • Damaged nerves
  • Damaged blood vessels

You might not have surgery until 1 to 3 weeks after you’re hurt, to allow time for the swelling to go down. While you wait, you’ll need to wear a splint, keep your leg raised, and put ice on the injury.

Your surgeon may do arthroscopic knee surgery. This is done through small cuts made around your knee.

You might need “open” surgery, with bigger cuts. The type you need depends on the damage to the rest of your knee.

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How Long Will Recovery Take?

After surgery, you may wear different knee braces as you heal. Some let you bend your knee -- to ease stiffness.

After you’re finished wearing splints or braces, your doctor should send you to a physical therapist to rehab your knee. You’ll do exercises to strengthen the leg muscles around your knee and work to bring a full range of motion back to your joint.

You may need to rehab your knee for up to a year. Athletes who dislocate their knees may be able to return to their sports, but they might not be able to perform at the same level as before.

WebMD Medical Reference from eMedicineHealth Reviewed by Lisa Bernstein, MD on December 29, 2016

Sources

SOURCES:

National Institute of Arthritis and Musculoskeletal and Skin Diseases: “Handout on health: Sports injuries.”

Journal of Athletic Training: “A review of knee dislocations.”

The Bone & Joint Journal: “Dislocation of the knee.”

Mayo Clinic: “Dislocation causes,” “Dislocation symptoms,” “Dislocation basics: Treatment and drugs.”

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