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Dislocated Knee Cap (Patella)

What is the patella?

The patella or knee cap is the small bone located in front of the knee joint. It protects the knee and connects the quadriceps muscles in the front of the thigh to the tibia.

The patella normally rests in a groove at the end of the thighbone (femur). When the knee bends and straightens, the patella moves up and down within the groove. The ends of the femur and the undersides of the patella are covered with a smooth substance called articular cartilage. This cartilage helps the bones glide easily along each other as you move your knee.

What is a dislocated knee cap (patella)?

Sometimes, the patella may slide too far to one side or the other, and pop out of its groove. When this occurs the patella can completely or partially dislocate. It is usually a result of trauma or a blow to the knee, but may happen with twisting the knee or landing badly from a jump.

When the patella dislocates, it is typically very painful. Often it pops back in by itself, but sometimes you may need help to get it back in. Even if the patella slips back into place by itself, it will still require treatment to relieve painful symptoms and loss of function.

What are the causes of patella instability?

Young, active individuals involved in sporting activities are most prone to patella dislocations. Once the patella has dislocated the first time, it is prone to recurrent dislocations.

Risk factors for patella instability may be related to the bones or the soft tissue, and often both. These include:

  • Improper muscle balance, leading to maltracking of the patella
  • Being loose-jointed (ligamentous laxity).
  • Damage to the knee ligament that holds the patella in place (the medial patello-femoral ligament)
  • Having a high knee cap.
  • Being born with a shallow groove for the knee cap (shallow trochlea).
  • Being knock kneed.

Treatment options for dislocated patella

Non-operative Treatment
Initial treatment for a dislocated patella includes:

  • Rest. Take a break from any sporting activities.
  • Ice. Use cold packs for up to 20 minutes at a time, several times a day. Do not apply ice directly to the skin.
  • Compression. To prevent further swelling, wear an elastic compression bandage.
  • Elevation. To reduce swelling, recline when you rest, and put your leg up on a pillow.

Physiotherapy is the mainstay of treatment once the knee has settled down from the acute injury. Specific exercises will strengthen the thigh muscles that hold the knee cap in place and help with correct tracking. Bracing may also help to keep the knee cap in the correct position.

Because a dislocation often damages knee tissues, the patella may remain looser, or more unstable, than it was before the injury. As a result, the patella may dislocate again.

Surgical Treatment

If your patella dislocates multiple times, or continues to be unstable despite therapy and bracing, surgery may be recommended to correct the problem. The type of surgery will depend on the cause of the unstable kneecap.

Surgical treatments often involve reconstructing the ligaments that hold the patella in place.

Surgery for patella dislocations

Surgery For Shoulder, Hip and Knee

Conditions For Shoulder, Hip and Knee

Perth
Albany

Enquiry

    Consulting Rooms

    Perth
    St John of God
    Medical Clinic
    Suite 213
    25 McCourt Street,
    Subiaco WA 6008

    Albany
    Great Southern
    Specialist Centre,
    55 Cockburn Rd ,
    Mira Mar WA 6330

    T: 08 9489 8733
    E: blakeney@wcortho.com.au
    Fax: 08 9489 8735

    Operating Theatres

    St John of God Hospital
    12 Salvado Rd, Subiaco WA 6008