Patellar Dislocation

Patellar Dislocation

Patella also called as kneecap which lies in front of knee joint and protects the joint.

In healthy individuals, upon flexion of the knee, the patella glides up and down a groove called the patella-femoral groove.

Quadriceps tendon is attached to patella. Patella increases the leverage of quadriceps muscles during knee joint movements such as straightening and extension.

Patellar dislocation is observed when the patella slips or moves outside this groove into the bony head of the femur (lateral femoral condyle). Knee injury most often causes patellar subluxation (partial dislocation).

Patellar dislocation often results from a severe blow or from a twisting action of the knee.

Patellar dislocation is initially treated with physical therapy and rehabilitation lasting six to sixteen weeks. Patient is advised to consider surgery if conservative treatment fails.

Most of the times after accidental dislocation the patella will move back to its normal position with straightening to the knee. Procedure is extremely painful and may need sedation.

Investigation for Patellar Dislocation:

X-ray will show the lateral dislocation of the patella. X-ray is also use to evaluate the displacement of osteochondral fragments, which may indicate emergency surgical treatment is necessary.

Frequent Patellar Dislocation: Recurrent patellar dislocation is mostly on lateral side and individuals will slide patella manually into normal position while extending their leg.

Risk Factors of Patellar Dislocation:

Insufficient Vastus Medialis Obliquus or VMO strength – The function of the VMO (vastus medialis obliquus) is to maintain the patella in its normal position within the patellofemoral groove by pulling it towards the center of the knee joint at the time of knee movements. This is known as ‘tracking’. If the muscles or its fibers are not strong or sufficiently oriented, then the patella becomes more prone to dislocate.

Q-angle – is the angle between femur or thigh and tibia or lower leg. 

Genu Valgus – Genu Valgus is anatomical abnormality of knee joint caused by increased Q angle. Patient suffering with genu valgus may push kneecap towards outside resulting in dislocation or subluxation (partial dislocation) while straightening their leg or when excessive force is applied to the inside of the knee.

Patella Alta – is a smaller size patella and it is a birth defects. The condition affects mobility and leg strength.

Treatment for Patellar Dislocation:

Conservative Treatments for Patellar Dislocations are:

  • Complete rest
  • Knee support like braces and ace crape bandage should used during activities
  • Anti-inflammatory Medication
  • Glucosamine 
  • Physical therapy to strengthen VMO
  • Cryo-therapy- apply ice over patella and knee

RICE therapy can be applied to the affected knee.


  • Arthroscopy to assess the extent of the injury.
  • Surgery – repair and remove loose fragment, repair structural damage.



  • 40-50% of conservatively treated patient will have recurring episodes of instability and some patients will require surgery. 
  • Chondromalacia patella is the common complication after patellar dislocation. Chondromalacia is inflammation of patella on inner surface and seen in sport injury.
Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 30, 2019

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