Patellar Instability or Kneecap Instability
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.
How does patellar or kneecap instability feel?
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.
How does kneecap or patellar instability happen?
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.
Who is at risk for knee subluxation and dislocation?
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:
- a shallow (or absent) groove on the trochlea or femur
- an abnormal insertion of the patellar tendon on the tibia (shin)
- knock knees
- high riding kneecap
How can patellar instability be fixed?
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.
Additional information on patellar or kneecap instability
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.