Patella Subluxation / Patella Dislocation

27 Aug Patella Subluxation / Patella Dislocation

Patella subluxation or patella dislocation is a common injury our physiotherapists see and help with.

What is the patella?

The patella is commonly known as the knee cap. 

It sits in a groove in the knee, which is called the ‘trochlear groove’.

Image reproduced from the American Association of Orthopaedic Surgeons, OrthoInfo.

What is a patella subluxation/dislocation?

This is where the patella (kneecap) moves out of it’s normal joint position (the trochlear groove that is sits in).

A patella dislocation is where the patella fully displaces out- it is completely out of the groove.

A patella subluxation (also described as a partial dislocation) is where the patella only partially displaces out of its normal alignment.

Commonly this occurs with the patella (kneecap) moving laterally or to the outside of the knee and may occur from:

  • Landing and twisting through the leg;
  • Direct trauma to the patella
  • Both types may result in damage to the structures that hold the patella in place. These structures that may be damaged include:

    • Medial retinaculum
    • Medial patellofemoral ligament (MPFL)

    As a result of the patella dislocating, the displacement of the knee cap may additionally cause:

    • Damage to the cartilage under the knee cap, known as osteochondral lesions.
    • A fracture in the bone, known as an osteochondral fracture.
    • Bony bruising or ‘bone oedema’, especially bone oedema the lateral femoral condyle (this is the outside of the knee where the patella can hit when it dislocates).
    • In some cases a loose body may form in the joint, known as a an intraarticular loose body.
    Image reproduced from: Diederichs, Gerd, Issever, Ahi S, & Scheffler, Sven. (2010). MR imaging of patellar instability: Injury patterns and assessment of risk factors. Radiographics, 30(4), 961-981.

    What are the signs and symptoms?

    • There will likely be an incident where the patient felt something “shift out of place of similar”.
    • There may be an audible “pop”.
    • There may be obvious distortion of the patella, “it looks out of place”.
    • Pain in the knee, particularly extending the knee and weight bearing through it.
    • Swelling in the knee.
    • A feeling of instability.

    Most subluxations and even dislocations will go back into place (which is called reduction). Often this happens spontaneously or by gently extending the knee. You should never try forcing the patella back yourself (as this can often cause further damage).

    How is it diagnosed?

    A patella subluxation or dislocation is diagnosed by understanding the history and mechanism of injury, observation and understanding the signs and symptoms.

    If needed, imaging may be used (such as an MRI or X-ray) to further ascertain the degree of injury.

    Do I need surgery?

    Some patella dislocations can be managed with a structured rehabilitation program without surgery, while sometimes surgery is needed first.

    Whether or not surgery is required will depend on several factors, including:

    • Whether there has been past dislocations
    • The degree of structural damage
    • The presence of any loose body or damage to the cartilage/bone

    What is the best management?

    Early management is often aimed at reducing pain and inflammation, and settling down the knee. This may include gentle mobility work and some basic strength work.

    The first aim of your rehabilitation will often be to restore full range of motion in the knee. You will also work on building the stability around the knee, particularly by strengthening the surrounding musculature.

    A physio can guide your rehabilitation:

    • Hands-on management (including massage, dry needling, stretching, mobilisation) to help reduce swelling and restore range of movement 
    • Progressive strengthening program
    • Balance and proprioception training
    • Gait, running and jumping re-training

    Correct and thorough rehabilitation will ensure you return safely to your chosen activity and help to prevent future problems with your knee.

    If you require help with your rehabilitation following a patella subluxation or dislocation, see our expert knee physios today Book Knee Physio

    If you want to read more about knee pain click this link Read more about Knee Pain