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Patella (Knee Cap) Instability

The patella lies at the end of the thigh bone, placed in a groove in the front side of the knee. The patella moves up and down the groove as the knee bends and straightens respectively. But at times, due to an injury or a hard fall, the patella might slide to the side to a large extent. This results in Patellar instability or patellar dislocation.

Causes of Patellar Instability:

  • An uneven groove in the thighbone can cause instability or dislocation.
  • Some people have looser ligaments. This makes their joints extremely flexible, causing it to be more prone to dislocation.
  • Patellar instability may be because of muscle weakness or malfunction.
  • Improper movements like running, jumping, climbing make the knee vulnerable to suffer from Patellar instability.

Knee Cap Dislocation

Symptoms of Patellar Instability:

patellar instability treatment

The knee looking out of shape due to knee cap dislocation

  • Pain in the knee.
  • The feel of the knee cap moving from one side to other.
  • Swelling and stiffness of the knee, causing restricted movement.
  • The knee looks deformed and out of shape.

Diagnosis of Patellar Instability:

Clinical examination mostly clinches the diagnosis. However an x ray would be necessary to confirm it. MRI scanning may be necessary in relevant cases to rule out additional injuries.

Knee Cap Dislocation

Xray knee showing patella in abnormal position

Treatment of Patellar Instability:

patellar instability treatment

A typical cylindrical cast used for managing knee cap dislocation

Usually a first time straight forward knee cap dislocation does not need surgery. The surgeon reduces the dislocation after giving pain medication with or without anaesthesia. After getting the knee cap into anatomical position a plaster is applied to the leg and left for 3 to 6 weeks depending on the severity of the injury. After the treatment normal activities are started gradually, with strengthening of specific group of muscles to prevent recurrence.

But if the Knee cap dislocates again and again then probably surgical reconstruction of the ligaments will rectify the problem. Most of the times the MPLF (Medial Patello-Femoral Ligament) is torn and it has to be reconstructed by using patients own ligaments. After a period of rest and physiotherapy patients can lead an active and normal life without any restriction of activity.

The torn MPLF (grey arrow) is reconstructed using patients own ligament tissue (red arrow).

Authored By Dr. Raj Kanna - Orthopaedic and Knee surgeon, Chennai

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