A patellar dislocation is when the kneecap (patella) slides out of the V-shaped groove in the front of the knee.
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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:
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Accessed February 18, 2021.
Last reviewed January 2021 by EBSCO Medical Review Board
Laura Lei-Rivera, PT, DPT
Last Updated: 2/18/2021