Dislocated Knee

Reviewed on 7/15/2022

Things to Know About a Dislocated Knee

Picture of knee dislocations plus ligament and artery damages. SOURCE: Medscape
Picture of knee dislocations plus ligament and artery damages. SOURCE: Medscape

What Is a Dislocated Knee?

A knee dislocation occurs when the bones that form the knee are out of place. A knee dislocation, more specifically, is when the bones of the leg (the tibia and fibula) are moved in relation to the bone in the thigh (femur). The bones of the knee are held together by strong bands of tissue called ligaments. Each ligament is responsible for stabilizing the knee in a certain position.

  • For a knee dislocation to occur, these ligaments must tear.
  • A partial dislocation is referred to as a subluxation.
  • In some injuries, the kneecap (patella) and its ligaments are also disrupted.

Inappropriate or delayed treatment of knee dislocation may result in loss of the leg.

What Are Symptoms and Signs of a Dislocated Knee?

  • A dislocated knee will always cause severe pain in the knee.
  • The knee will look deformed.
  • Sometimes, there will be no feeling below the knee.
  • If the knee relocates, it will become swollen from fluid in the knee and be painful with any movement.
  • Very serious symptoms include loss of a pulse below the knee or loss of feeling or movement below the knee.

What Causes the Knee to Dislocate?

Knee dislocations are rare. They usually happen only after major trauma, including falls, car crashes, and other high-speed injuries. If the knee is dislocated, it will look deformed. The usual straight line of the leg will be crooked or angulated. Sometimes, knee dislocations relocate (go back into place) on their own. In this case, the knee will be very swollen and painful. Even if the knee relocates, usually significant damage (tearing) of ligaments has occurred.

When Should You Call a Doctor If You Have Dislocated Your Knee?

If a dislocated knee injury is suspected, there is likely severe ligament injury. Go to the nearest hospital's emergency department. Seek care for these reasons:

  • Extreme pain or swelling after a serious injury (such as a car crash)
  • An obvious deformity of the knee
  • Numbness in the foot
  • No pulses in the foot

Go to the hospital's emergency department for medical care for a dislocated knee immediately.


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How Do You Know if You Have a Discloated Knee?

Depending on how the knee looks, the doctor will check the injury for proper diagnosis in the following ways:

  • X-rays: X-rays will be taken to make sure there are no breaks in the bone.
  • Examination of pulses: Injury to the arteries in the knee is common with this injury. The doctor will make sure there are pulses in the foot.
  • An arteriogram (X-ray of the artery): This X-ray may need to be done to detect injuries to the artery. Some medical centers may also use special ultrasound or Doppler (sound wave) machines to assess the blood flow in the arteries.
  • Examination of nerves: Nerves also run through the knee, so it is possible that they may have been damaged. The abilities to feel touch and move certain muscle groups are the main ways nerves are tested. Specifically, the ability to move the foot up and down and to turn the foot inside (inversion) and outside (eversion) are important muscle movements to examine. Any feeling of numbness is concerning for nerve injury.

What Can You Do for the Pain and Swelling of a Dislocated Knee?

This injury should not be cared for at home. It is best to get medical care as soon as possible. Placing ice on the injured area may help for some pain control and to decrease some of the swelling. But the most important treatment is to have a doctor assess the injury and relocate or put the knee back in place.

What Is the Treatment for a Dislocated Knee?

Relocation: The doctor will move your lower leg back into position, a process called reduction. Most doctors will do reduction after a person has been given pain medication or is given "conscious sedation," where the patient is sedated enough to withstand the discomfort of relocation but not completely sedated. Relocation is an important early step in repairing damage to nerves, blood vessels, ligaments, and other tissues of the knee. Relocation is usually done by emergency and orthopedic doctors.

Surgery: If an arterial injury is determined to be present, immediate surgery by trauma or vascular surgeon to repair the injured vessel(s) and maintain blood flow to the leg is necessary.

Immobilization: To avoid further injury and to help with the beginning of healing, the entire knee joint will be kept in a splint or immobilizer. This will keep the knee from bending and help the tissues to start healing.

Referral: A dislocated knee almost always has severe tears and sprains of the ligaments and sometimes has breaks in the bones of the knee. After swelling has gone down, the knee may need reconstruction surgery to regain function. A bone specialist (orthopedist) will need to see you after this injury.

After the procedure, the knee should be immobilized with bracing or casting, and the patient will be given crutches. Do not put weight on the affected leg. Elevate the leg as much as possible, and follow up with your orthopedist.

What Is the Recovery Time and Prognosis for a Dislocated Knee?

In general, this is a very serious injury. Recovery is possible, but often the injured knee does not regain its previous capacity to adsorb stresses. It is not uncommon for doctors to recommend some types of supportive wraps or devices to protect the knee and reduce stress on it, especially during activities like skiing or playing football. Some knee dislocations cause so much damage that some doctors will suggest that certain activities are avoided altogether.

Almost all knee dislocations require reconstruction surgery because major injury to the artery occurs in many knee dislocations and because of the severe ligament injury. After appropriate treatment and surgery, however, results have been good. Knees return close to normal in most cases. Chronic pain is a common problem. The prognosis is best with an optimal rehabilitation exercise program.

How Can You Prevent from Dislocating a Knee?

Attempt to avoid major accidents. Avoid risky activities such as skiing, motorcycle riding, or jumping from high places; people who decide to do these high-risk activities should obtain and follow instructions from experts about how to decrease their risks.

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A dislocated knee is a rare injury that causes severe pain and deformity.

Causes of Knee Pain

Dislocated Knee

Knee dislocation

  • Description: Dislocation of the knee is a true limb-threatening emergency. This is also a rare injury. Dislocation of the knee is caused by a particularly powerful blow to the knee. The lower leg becomes completely displaced with relation to the upper leg. This displacement stretches and frequently tears not only the ligaments of the knee but also arteries and nerves. Untreated arterial injuries leave the lower leg without a blood supply. In this case, amputation may be required. Nerve injuries, on the other hand, may leave the lower leg viable but without strength or sensation.
  • This injury can be due to a motor vehicle accident where the patient's knee or leg hits the dashboard.
  • Symptoms and signs: Knee dislocations are severely painful and produce an obvious deformity of the knee. Many dislocations are reduced or put back into anatomic alignment spontaneously. As this occurs, many will report feeling a dull clunk.
Reviewed on 7/15/2022
Kelleher, HB, MD, et al. Knee Dislocation in Emergency Medicine. Medscape. Updated Aug 24, 2015. <http://emedicine.medscape.com/article/823589-overview>.