by Cynthia M. Johnson, MA
A patellar dislocation is when the kneecap (patella) slides out of the V-shaped groove in the front of the knee.
It may be caused by:
This problem is more common in active children and young adults under 20 years of age. It is also more common in athletes and people in the military.
Other things that may raise the risk are:
Other problems that can create instability in the patella are:
Problems may be:
The doctor will ask about symptoms and past health. You may be asked how the injury happened. A physical exam will be done. It will focus on the knee. This may be enough to make the diagnosis.
Images may be taken of the knee. This can be done with:
It may take up to 6 weeks to recover. The goals of treatment are to put the knee back into the V-shaped groove and to manage symptoms.
The doctor will move the knee back into place. Other treatment may include:
People with a repeat or severe injury or those who are not helped by other methods may need surgery. Options are:
This injury is due to an accident. These are hard to prevent.
Family Doctor—American Academy of Family Physicians
Ortho Info—American Academy of Orthopaedic Surgeons
Canadian Association of General Surgeons
Canadian Orthopaedic Foundation
Acute patellar dislocation. EBSCO DynaMed website. Available at: https://www.dynamed.com/condition/acute-patellar-dislocation. Accessed February 18, 2021.
Duthon VB. Acute traumatic patellar dislocation. Orthop Traumatol Surg Res. 2015 Feb;101(1S):S59-S67.
Unstable kneecap. Ortho Info—American Academy of Orthopaedic Surgeons website. Available at:
...(Click grey area to select URL)
Accessed February 18, 2021.
Last reviewed January 2021 by EBSCO Medical Review Board Laura Lei-Rivera, PT, DPT
Last Updated: 2/18/2021
EBSCO Information Services is fully accredited by URAC. URAC is an independent, nonprofit health care accrediting organization dedicated to promoting health care quality through accreditation, certification and commendation.
This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.
To send comments or feedback to our Editorial Team regarding the content please email us at email@example.com. Our Health Library Support team will respond to your email request within 2 business days.