Patellar subluxation or dislocation (3045)

Key points below

What are patellar subluxation and dislocation?

If the knee cap (patella) moves to the outside of the knee but pops back in on its own, it is called subluxation. There may be rare times when the patella moves to the inside of the knee. 
If the knee cap moves away from the knee joint and needs help 

to move back in, it is called dislocation.
It may be caused by:
Trauma such as being hit in the knee. 
A sudden movement or twist of the knee. 
Being born with poor muscle strength or a poor knee knee angle.  This is called congenital.

What are the symptoms?

Front (anterior) knee pain.  
Pain on the inner (medial) side of the knee.
The knee cap will feel unstable. 
The knee cap will most likely have too much outward (lateral) movement with squatting and knee extension.
With walking and other weight bearing activities the knee may feel as though it is 
If it is dislocated, the knee cap will look out of place.  

How is it diagnosed?

Your healthcare provider will review your activities. It is diagnosed by the location of the pain, symptoms and a physical exam.  An X-ray may be done to make sure the knee cap is in the right place.  It will also help rule out any type of broken bone or fracture. 

How is it treated?

Pain medicine, decreased activity, resting and icing of the knee may help with pain and swelling.  Other treatments may include: 
Protection.  A sleeve with lateral support to keep the knee cap from moving.  
Icing.  Use a bag of crushed ice, or frozen peas or corn.  You can reuse these items as an ice pack.  Do not eat the corn or peas once they have been used as an ice pack.
Put a towel between skin and bag. If you put the ice pack directly on the skin, it may cause frost bite.  
Put the bag on the sore area.  
Leave on for 15 to 20 minutes.
Exercises to stretch and strengthen may start as directed by the healthcare provider. They will also need to be done at home.  Regular therapy helps you learn an exercise routine. This will help you get back to regular activities. 

What follow-up is needed?

A follow-up with the doctor is needed to make sure the knee has healed and is aligned properly.  An X-ray to view the alignment may be done.  


Call your child’s doctor, nurse, or clinic if you have any questions or concerns or if your child has special health care needs that were not covered by this information.