Patella Fracture: Causes, Diagnosis and Treatment

Patella fracture is a injury the involves the patella bone which is located in the front of the knee joint. While sitting on a chair put your hands over your knees. The roughly round to triangular bone that you feel is your patella.

The patella is a sesamoid bone.This means that it is located within a tendon.

It would good to first check out the Knee anatomy before proceeding further so that you may get a better understanding of patella fracture. (skip this if you have already done so)

The tendon of the quadriceps muscle forms an expansion as it crosses the knee joint. The patella bone is located in the center of this tendon. Extending from the lower pole of the patella is the patellar tendon that attaches to the tibial tuberosity.

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photo of knee joint

Function of the patella is to

  • increase the leverage of the quadriceps muscle
  • protect the quadriceps and patellar tendons

Fractures of the patella are more common in males between the age of 20 to 50 years. They are caused by

  • direct injuries such as falling on the knee or road traffic accidents
  • indirect injuries from sudden contraction of the quadriceps muscle

Symptoms include

  • pain
  • swelling over the knee; swelling may be mild or absent in hairline or undisplaced fractures
  • inability to walk; sometimes patient may be able to walk with difficulty in these fractures
  • inability to extend the knee against gravity (raise the leg straight) may be present
  • in hairline fractures the only symptom may be tenderness over the patella bone
  • swelling develops rapidly in displaced (fragments separated) fractures of the patella as blood fills up the knee joint

Diagnosis is by x rays of the knee joint. X rays will help in the classification of the fracture. Skyline view x rays may be required sometimes.

x ray of comminuted patella fracture

This x ray of patella fracture shows 3 pieces of bone, but during surgery there were 4 pieces. One piece was of cartilage. In the x rays below, taken 6 weeks after surgery, the same fracture was fixed by stainless steel wires and is healing well.

patella fracture patella fracture

Classification is according to the pattern of the fracture.

  • Transverse in which the fracture occurs through the mid line dividing the bone into two parts upper and lower.
  • Longitudinal in which there is a vertical split in the bone
  • Lower or upper pole fractures
  • Comminuted fractures in which there are multiple pieces
  • Osteochondral fractures that involve the cartilage

Classification of patella fracture is also according to the separation of the bone fragments.

  • Displaced fractures in which the bone fragments are separated
  • Undisplaced fractures in which the bone fragments are not separated

So there can be a displaced transverse fracture or a undisplaced vertical fracture etc, when the two classifications are combined.

patella fracture classification

A type of osteochondral patella fracture that occurs in children is called a sleeve fracture. In this fracture one of the fragments of the fracture is mainly or entirely made of cartilage. This fracture occurs due to a sudden contraction of the quadriceps muscle. It is usually seen during high, long jump and other games that require jumping such as basketball.

This fracture has is difficult to recognize on x rays and can be missed. It should always be suspected when examining a child with a knee injury.

Treatment depends upon the following factors

  • fracture is displaced or undisplaced
  • you are able or unable to lift your leg straight against gravity

Treatment includes the following methods

  • ankle to groin plaster cast
  • surgery which includes the following
    1. fracture is aligned and fixed with stainless steel wires or screws called tension band wiring
    2. few fracture fragments are removed and the remaining bone is stitched with the tendon called partial patellectomy
    3. all the fracture fragments are removed and the tendon ends are stitched together called total patellectomy

Undisplaced fractures in which it is possible to lift the leg against gravity are treated with a plaster cast.

Undisplaced fractures in which it is not possible to lift the leg against gravity are treated by tension band wiring.

Transverse or longitudinal displaced fractures require surgery in which the fracture is fixed by wires or screws.

Communited fractures (multiple pieces) require,partial patellectomy.

Severely communited fractures may require total patellectomy if they are un-salvageable.

Latest trend is to attempt to save as much of the patella as possible even in fractures with multiple bone pieces by gently holding the pieces in proper position and fixing them with flexible and stiff wires.

If part or whole of the patella is removed then a plaster cast is given for 6 weeks to allow good healing of the patellar or quadriceps tendon

Complications include

  • stiffness of the knee joint
  • infection
  • arthritis

This is a x ray of a 11 year old girl who sustained a osteochondral fracture following fall from a roof. Initially it was suspected to be a sleeve fracture but during surgery it turned out to be a large and loose bone piece (yellow arrow) with cartilage. It was reattached with sutures.

patella fracture lower pole

This is a x ray of a patient with a fracture of the lower pole of patella. In the following x ray you can see the same fracture treated by tension band wiring method.

patella fracture lower pole

patella fracture with many pieces patella fracture with many pieces

This is a x ray of a patient with a fracture patella with multiple pieces, which he sustained from a fall from height. During surgery all the small pieces were removed and the two major pieces were stabilized by tension band wiring (see below). The loose pieces were then used as bone graft to fill a defect in the outer or superficial part of the patella. So, now he has a slightly smaller patella. His recovery was good.

patella fracture after surgery

Frequently Asked Questions

How long does the fracture take to unite?

It takes 4 to 6 weeks to unite.

How long does it take to reach the activity and strength level as before the fracture?

It can take 8 months to a year to reach the the pre-fracture level with out physiotherapy.

If you want to return quickly to the pre-fracture level of activity following a patella fracture you need intensive physiotherapy at home or at a physiotherapy center.

How can knee stiffness be prevented?

Stiffness is seen more in

  • knees with arthritis (more age)
  • fractures with multiple pieces
  • fractures requiring removal of part or whole of patella
  • immobilization in a plaster cast after surgery

The best way to prevent stiffness is to fix the fracture securely allowing early mobilization of the knee after surgery and start physiotherapy regularly.

I hope the information provided was helpful. If you have any query about patella fracture you can ask me at the contact me page.

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This page was last updated on 2nd March 2011.


Other causes of knee pain include...

Knee Osteoarthritis

Knee Bursitis

Meniscal Injury

Ligament Injury

Knee Fracture

Tibial Plateau Fracture

Osgood Schlatter Disease

Knee Anatomy

Knee Replacement Surgery

Go back from Patella Fracture to Knee Pain




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