What is patellar instability or kneecap instability? In the front of the knee, the kneecap slides up and down in a groove in the thigh bone. Sometimes, it can slip out causing pain, swelling, and cartilage injury.
It can feel unstable and in severe cases it can be difficult to fully extend the knee. Sometimes patients have to go to the ER to get the patella back into the groove. Often, these injuries are accompanied by swelling and it can take weeks to months to feel normal again.
In some patients it happens without any trauma and at a young age. In others, unfortunately, it can occur playing sports with or without a contact injury. It can recur, especially when it first happens before the age of 25.
Both young women who are loose jointed and female athletes who experience a traumatic dislocation while playing their sport are at risk for subluxation and dislocation. Additionally, although subluxation and dislocations do occur in men and boys, it happens much less frequently. Common risk factors include:
In most cases it can be fixed by reconstructing the MPFL (Medial PatelloFemoral Ligament), which is a minimally invasive surgery with a 4-6 month recovery. In patients who have suffered cartilage damage the surgery may be more complicated with the addition of a bone re-aligning surgery such as a tibial tubercle osteotomy and/or a cartilage replacement surgery.
For more information about patellofemoral instability (also known as patellar instability or kneecap instability), check out this article on the Hospital for Special Surgery website. You can also download this information about patellofemoral instability.