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Dislocated Kneecap

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Last updated October 1, 2020

Dislocated kneecap questionnaire

Use our free symptom checker to find out if you have dislocated kneecap.

The kneecap (patella) is the bone that covers the knee joint. Abnormalities in the support structure of the knee and unusual forces can cause a dislocated kneecap.

Dislocated kneecap questionnaire

Use our free symptom checker to find out if you have dislocated kneecap.

Dislocated kneecap symptom checker

What is a dislocated kneecap?

A dislocated kneecap is when the bone that covers the knee joint, the kneecap or patella, is moved out of place. The kneecap is normally held in place by tendons that connect it to muscles around the knee joint. Dislocation can be caused by planting the foot and twisting a flexed knee, direct trauma to the knee, or hyperextending the knee.

Symptoms include a feeling of the knee "giving way," severe knee pain, a limited range of motion of the knee, as well as swelling or a dislocation that is a noticeable bulge in the leg.

Treatments include pain medication, manual or surgical reduction of the knee, rest and at-home remedies, and physical therapy and rehabilitation.

You should visit your primary care physician within the next 24 hours. The first step is to return the kneecap to its proper place, a process called reduction.

Symptoms of a dislocated kneecap

There are a few main symptoms of a dislocated kneecap that most people will experience as well as a few others experienced by some people with this condition.

Main symptoms

The main symptoms experienced by people with a dislocated kneecap include:

  • A feeling of the knee "giving way": Most people who develop a dislocated kneecap will experience a feeling of the knee "giving way" at the time of the dislocation. They may feel or hear a pop or tear at the time of the dislocation.
  • Severe knee pain: Shortly after the dislocation, most people will experience severe knee pain. The pain may prevent the affected leg from bearing any weight. The knee may also be tender when pushed on, especially along the edges of the kneecap.
  • Limited range of motion of the knee: The position of the kneecap keeps the knee from bending normally if it is dislocated. The knee is usually stuck in a position that is bent at 20 to 30 degrees.

Other symptoms

Some people can also experience the following with a dislocated kneecap:

  • Swelling of the knee: This swelling is usually caused by fluid that accumulates in the knee joint due to inflammation after the dislocation, but in some cases, it may be due to blood collecting in the knee joint.
  • Noticeable abnormal location of the kneecap: This is most common when the kneecap is dislocated to the outside of the leg, as it will look like a bulge on the outer side of the knee.

Dislocated kneecap questionnaire

Use our free symptom checker to find out if you have dislocated kneecap.

Dislocated kneecap symptom checker

Causes of a dislocated kneecap

Abnormalities in the support structures surrounding the kneecap or unusual forces to the knee can cause dislocation. The kneecap can dislocate in several different directions; most commonly, to the outside of the leg. Specific causes of a dislocated kneecap include planting the foot and rotating a flexed knee, direct trauma to the knee, and hyperextension.

Planting the foot and rotating the leg while the knee is flexed

Planting the foot and rotating the leg while the knee is flexed is the most common cause of a dislocated kneecap. When the knee is bent, the kneecap is usually pushed toward the outside of the leg. Suddenly twisting the leg while the leg is in this position may cause the kneecap to dislocate to the outside of the leg. This may be seen in sports such as gymnastics, running, ice skating, basketball, tennis, baseball, or softball.

Direct trauma to the knee

The direction of the trauma to the knee and the position that the leg is in when the knee is hit will determine which way the kneecap dislocates.

  • From the inside or outside: Direct trauma to the inside of the knee will usually cause the kneecap to dislocate outward, while direct trauma to the outside of the knee may cause the kneecap to dislocate inward.
  • From above or below: Trauma to the knee from above or below while the knee is bent can cause the kneecap to dislocate into the knee joint, which is a more serious form of a dislocated kneecap.

Hyperextension of the knee

Hyperextension of the knee — straightening the knee more than it normally should move — can cause a dislocated knee in rare cases. This is more common in older people who may have a degenerative joint disease.

Who is most likely to be affected

Kneecap dislocations occur more frequently in:

  • Teenagers and young adults who engage in sports activities
  • Overweight individuals
  • Older people with a degenerative joint disease

Dislocated kneecap questionnaire

Use our free symptom checker to find out if you have dislocated kneecap.

Dislocated kneecap symptom checker

Treatment options and prevention for a dislocated kneecap

Several treatment options exist for a dislocated kneecap, depending on the type and severity of the dislocation. In some cases, the dislocated kneecap may spontaneously reduce (return to its normal position) from straightening the leg. In other cases, a physician may need to use certain maneuvers or even surgery to reduce the dislocated kneecap. Other treatments may include pain medication, at-home remedies, and physical therapy and rehab, described below.

Pain medication

Because dislocated kneecaps tend to cause a lot of pain, most people with dislocated kneecaps will need pain medications to control the pain and allow for the kneecap to be put back in place. Pain medications may be given through an IV and may include morphine or fentanyl, among others.

Manual reduction of the kneecap

People with dislocated kneecaps that do not spontaneously return to the proper position may need a maneuver to manually reposition the kneecap.

  • Timing: This can be done immediately following the dislocation if it is witnessed, or later after administration of pain medications.
  • Details: The individual is placed on his or her back with the hips bent and the physician slowly straightens the leg while pushing inward on the kneecap to return it to its normal position.

Surgery to reduce the kneecap and repair tendon damage

Surgery to reduce the kneecap and repair any damaged tendons or ligaments may be required — especially in people whose kneecaps cannot be manually reduced or whose kneecaps were dislocated into the joint space.

Rest and at-home treatments

After the dislocated kneecap has been successfully reduced, the physician may recommend the following. The main methods can be remembered by the mnemonic RICE:

  • Rest: This can be achieved by limiting standing, walking, or repeated bending.
  • Ice: Apply ice to the knee to reduce swelling.
  • Compression: Try wrapping the knee with bandages.
  • Elevation: Try to elevate the knee above the level of the heart.
  • Additional bracing: The knee may be placed in an immobilizer or a brace while it recovers.

Physical therapy and rehabilitation

Following treatment of the dislocated kneecap, most people will benefit from a course of physical therapy and rehabilitation to help strengthen the muscles around the knee and improve the outcome.

When to seek further consultation for a dislocated kneecap

If you experience any symptoms of a dislocated kneecap, such as feeling the knee give way, severe knee pain, an inability to bend the knee, or an abnormal location of the kneecap, you should go to your physician or emergency department. A physician can examine your knee to see if you have a dislocated kneecap and help return the kneecap to its proper position.

Questions your doctor may ask to determine dislocated kneecap

  • Is your knee pain constant or come-and-go?
  • Is the knee pain affecting one or both knees?
  • How severe is your knee pain?
  • Which of these if any make your knee hurt worse?
  • How long has your knee pain been going on?

Self-diagnose with our free Buoy Assistant if you answer yes on any of these questions.

Hear what 1 other is saying
Dislocated kneePosted June 7, 2021 by T.
Dislocated knee 4 months after a complicated knee revision. This revision left me with almost 90% of my leg having titanium rods in it. Because of the position I was in, I not only dislocated my knee but also broke all four bones in my knee. Now, mind you, this is a Work Comp case. That in itself should tell you something. This happened February 8th. Because the only specialist at the time did not accept W.C., I was sent back to the Dr who did my revision. The Dr. who told me on the phone the day it happened that he was not qualified to handle this type of injury. But here I am. It's June 7th and nothing has been done. All 4 bones are still broken. One clearly from the X-ray in approximately 6 pieces..... Not one word being said about the fact that my patella is sitting on my prosthetic knee at a very bad angle. Everything I have resumed doing has told me that the ligaments and tendons are torn. I'm not understanding why here in California there seems to be no specialist to be found who could help me with this. It seems not one Dr. involved cares enough to research Dr.'s who take W.C. or who would be willing to go in the W.C. system to save my leg. I have been in the W.C. system for 19 years. Approximately 20 + surgeries. I have had Dr.'s accommodate me and wanting to help by joining the W.C. system to do the best for me. I'm so frustrated at this point. Can I get any feedback on what to do from here! Please.
Dr. Rothschild has been a faculty member at Brigham and Women’s Hospital where he is an Associate Professor of Medicine at Harvard Medical School. He currently practices as a hospitalist at Newton Wellesley Hospital. In 1978, Dr. Rothschild received his MD at the Medical College of Wisconsin and trained in internal medicine followed by a fellowship in critical care medicine. He also received an MP...
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References

  1. Kneecap dislocation. U.S. National Library of Medicine: MedlinePlus. Updated December 6, 2018. MedlinePlus Link
  2. Dislocated kneecap. NHS. Updated June 16, 2016. NHS Link
  3. Patellar dislocation and instability in children. American Academy of Orthopaedic Surgeons: OrthoInfo. Updated March 2014. OrthoInfo Link
  4. Kneecap dislocation - aftercare. U.S. National Library of Medicine: MedlinePlus. Updated December 6, 2018. MedlinePlus Link
  5. Patellar instability/kneecap dislocation (pediatric). ColumbiaDoctors. ColumbiaDoctors Link
  6. Smith TO, Donell S, Song F, Hing CB. Surgical versus non-surgical interventions for treating patellar dislocation. Cochrane. Published February 26, 2015. Cochrane Link