Patella dislocation

What is a patella dislocation?

A dislocated patella (kneecap) is a common injury.

The patella sits at the front of the knee and slides up and down inside a vertical groove (trochlea) at the bottom of your thigh bone (femur) as you bend and straighten your knee. Multiple tendons and ligaments secure the kneecap within the groove as you move your knee.

When the kneecap dislocates, it will come out of this groove, frequently tearing the muscles and ligaments. Often the kneecap will go back into the trochlea groove spontaneously, but sometimes it needs to be put back into place at the hospital under sedation (this process is called a reduction).

X-ray photo of normal kneecap position
X-ray showing a dislocated kneecap

What are the causes of a patella dislocation?

Patella dislocations usually occurs by direct impact or a sudden pivoting injury.

However, it doesn’t always take a lot of energy to sustain a dislocation – it can also be due to variety of other factors such as muscle imbalance/weakness, general joint laxity (hypermobility) and normal variations in the way your knee joint is built, that all predispose you to kneecap dislocations.

Furthermore, if you’ve had a previous patella dislocation, the ligaments securing the kneecap may not be functional, which can lead to recurrent patella dislocations.


A dislocated kneecap will need to be put back into place, either by gentle straightening of your knee, or with the help of a health professional.

For a first-time dislocation, the treatment is usually non-surgical, with a short period of bracing and referral to physiotherapy.

Physiotherapy is very important. Your physiotherapist will provide a targeted rehabilitation program that will focus on stretching tight structures, strengthening muscles that restrain the kneecap, and improve your position and movement control (proprioception).

However, if you have injured any other structures at the time of your first kneecap dislocation, such as cartilage injury, fracture, or loose bodies in the knee, I may recommend surgery to manage these problems acutely.

If you have recurrent dislocations despite thorough rehabilitation, especially if you have normal variations in the shape of your knee which predispose you to further dislocations, then surgery may be recommended.

Depending on your symptoms and predisposing factors to patella instability, I will recommend any combination of the following:

  • Key hole surgery to remove loose bodies
  • Repairing ligaments
  • Reconstructing the ligaments that restrain your kneecap with tendon grafts
  • Improving the position of your kneecap within the groove by repositioning the tibial tubercle (a bony bump on the front of the shin bone where your kneecap tendon attaches to).


Most patients will recover fully within 3 months with proper rehabilitation. Re-dislocation rates with non-surgical treatment is between 15-50% based on available research literature.

Re-dislocation rate is highest in those who sustain their first dislocation under the age of 20.


Anterior Cruciate Ligament (ACL)


High Tibial Osteotomy




Patella Dislocation

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Elmwood Orthopaedics
Level 3, 11 Caledonian Road
Saint Albans, Christchurch 8014