Types of Patella Fractures

NYU Langone doctors can identify the many types of fractures that can occur in the bones that form the knee joint. One of the more common types is a fracture of the patella, or kneecap, which is the round, movable bone located in the front of the knee. A fracture can occur in any part of the patella and can vary in severity from a shallow crack to a break that splits the bone into separate pieces.

Symptoms of a fractured patella include sharp pain around the kneecap, especially when you attempt to bend the knee or kneel. The area surrounding the injured knee may be red and swollen. Most people recover fully and regain full knee function after being cared for by an orthopedist.

The experts at NYU Langone Orthopedic Hospital classify patella fractures according to the following definitions in order to determine the most effective treatment plan.

Closed Fracture

Most types of patella fractures are closed fractures, in which the patella does not break through the skin. Some types of closed fractures may be treated without surgery.

Open Fracture

An open fracture occurs when the broken bone breaks through the skin, exposing the injured patella. An open fracture around the knee always requires immediate, emergency care and corrective surgery.

Nondisplaced Fracture

This type of fracture occurs when a bone breaks into two or more pieces but the pieces do not separate and the fragments remain in place. Nondisplaced fractures are usually closed fractures.

Displaced Fracture

If the patella breaks into two or more separate pieces that don’t remain in contact with each other, the break is called a displaced fracture. This type of fracture may occur in any part of the patella, and the bone may break vertically or horizontally. A displaced fracture may be a closed or open fracture.

Types of displaced fractures include simple, comminuted, and osteochondral fractures.

Simple Fracture

A simple fracture is a closed fracture in which the bone breaks into two pieces and is either nondisplaced or easy to put back together. 

Comminuted Fracture

If the bone shatters into more than two pieces that don’t stay in place, the fracture is called a comminuted fracture. A comminuted fracture may be a closed or open fracture. 

Osteochondral Fracture

A displaced fracture may also occur in the layer of cartilage at the bottom of the patella, where it connects with other bones in the knee joint. Cartilage is a smooth material that lines the ends of the bones in joints to prevent bones from rubbing against one another during movement. An injury to this cartilage and the underlying bone is called an osteochondral fracture. Typically, this injury is a closed fracture. 

All types of patella fractures may damage cartilage and therefore increase the risk of osteoarthritis, a degenerative condition of the joint that is characterized by cartilage damage. Because osteochondral fractures always affect cartilage in the knee, people with osteochondral fractures are at an even higher risk of osteoarthritis of the knee.