Patella Fracture (Broken Knee Cap)

The patella is the small bone that sits at the front of your knee that connects the muscles in the front of your thigh to your tibia. It also acts as a shield for your knee joint, which makes it vulnerable to fractures, especially if you fall directly on your knee. A patella fracture is a serious injury that can make it difficult or impossible to fully straighten your knee or walk.


Patella fractures can be simple and clean two-piece breaks or they can shatter into many pieces. Breaks can also occur at any part of the bone and can sometimes fracture in more than one area. There are four main types of patella fractures. These include:

  • Stable fracture: In this type of fracture, the pieces of the bone might still be in contact with each other or be separated by only a millimeter or two. The bones typically stay in place during the healing process.
  • Displaced fracture: The broken ends of the bone are separated and do not line up correctly in this fracture. The joint that is typically smooth may be disrupted as well. Surgery is usually required to put the pieces of bone back together.
  • Comminuted fracture: With this fracture, the bone shatters into at least three pieces. It could be a stable or unstable fracture depending on the pattern of the fracture.
  • Open fracture: This kind of fracture causes the bone fragments to stick out through the skin. These fractures often involve damage to the soft tissues around the kneecap, which may take longer to heal. These types of fractures require immediate medical attention as there is a significant risk of infection. 

Causes of Patella Fractures

Typically, there are two main causes of patella fractures. The first is falling directly onto the kneecap, causing it to shatter. The second is receiving a sharp blow to the knee. One common way this occurs is with head-on vehicle collisions, as your kneecap may be driven into the dashboard.

There can also be indirect causes of patella fractures, although these are less common. For example, a sudden contraction of your quadriceps muscle can pull apart the patella.

Symptoms of Patella Fractures

The most common symptom you will experience with a patellar fracture is pain and swelling in the front of your knee. You may also experience visible bruising. Perhaps the most recognizable symptom is an inability to straighten the knee or an inability to walk.

Treatment for a Broken Knee Cap

There are both nonsurgical and surgical options for treatment depending on the severity of your fracture.

If the bone pieces have not been displaced, surgery may not be necessary. Instead, a cast or splint may be applied to keep your knee as straight and stationary as possible. It will allow your bones to stay in the correct position while they heal. Sometimes you might be able to bear weight on your leg while you wear a cast or brace. Other times, you might not be allowed to bear any weight for 6-8 weeks.

You’ll likely need surgery if the pieces of the knee cap are out of place. When the bones are not close together, they have difficulty healing. The procedure your doctor recommends will depend on what kind of fracture you have.

Transverse Fracture 

These are two-part fractures. They are usually fixed in place with screws or pins and wires and a figure-eight configuration tension band. The band presses the two pieces together. This procedure works best for fractures near the center of the patella because pieces at the ends of the kneecap are too small.

Comminuted Fracture

This kind of fracture occurs when the kneecap is pulled apart from the injury before getting crushed when the person falls on it. The result is bone fragments that are too small to be put back in place. The doctor will remove those pieces and reattach the loose patellar tendon to the remaining patellar bone. 

If the kneecap is broken at its center and the pieces are separated, a combination of wires and screws may be used to fix it. Removing the kneecap completely is only used as a last resort.

Patella Fracture at OAR

The severity of patella fractures can vary widely, which is why it is always advisable to see a doctor if you think one has occurred. The team at OAR is committed to providing you with the highest quality orthopaedic care for all injuries, including patella fractures.