Diagnosing Patella Fractures

A patella fracture occurs when there is a break in the round, movable bone at the front of the knee called the patella. The bone is also commonly known as the kneecap. The patella lies within a large tendon, called the quadriceps tendon, which connects the thigh muscles to the lower leg bone. The patella helps absorb stress put on the legs during physical activity, especially during walking, running, and climbing stairs.

Most patella fractures occur as the result of a fall—but not because of direct impact with the ground. In the split second after your body recognizes you are falling, the muscles above the knee quickly contract in an attempt to straighten the knee and break the fall. Sometimes this muscle contraction, called an eccentric contraction, is so strong that the force overwhelms the patella, breaking it before the knee even hits the ground.

Less commonly, a fracture may occur because of a sharp blow to the patella as a result of a car accident or other high-force trauma. Many patella fractures in New York City occur when pedestrians are struck by cars while crossing a street. Even at low speeds, the impact of a car’s front bumper on the patella can cause a fracture.

Orthopedic specialists at NYU Langone can quickly and accurately diagnose a fractured patella and identify the type of fracture that has occurred. Depending on the severity of the break, a fractured patella can be painful and may make walking difficult or impossible. If a knee injury causes debilitating pain, or if the bone protrudes through the skin, doctors recommend seeking immediate care at an emergency room. Less painful or less severe knee injuries can be diagnosed in the doctor’s office.

For all knee injuries, NYU Langone doctors conduct a physical exam to confirm the presence of a fracture and assess symptoms and signs, such as tenderness, swelling, and disfigurement. Often, the doctor needs more detail about the extent of a fracture—for example, whether a bone fragment has separated from the patella—and may confirm diagnosis by taking detailed images of the knee.

Physical Exam

Doctors at NYU Langone examine the knee, assessing the amount of swelling and disfigurement, and ask about the type and severity of pain you’re experiencing. An open fracture is visible immediately, as the bone protrudes through the skin. Open fractures always require surgery. If you injure your knee and can see the bone, it is important to go to an emergency room for immediate help.

For closed fractures, in which the bone fragments remain beneath the skin, the doctor asks questions about how the injury occurred, how much pain you feel, and exactly where the pain is located. You may be asked to extend or flex your leg as much as possible, so that the doctor can evaluate whether other tendons, ligaments, or bones are injured.

During an exam, the doctor also asks questions about your medical and family history. Information about other medical conditions or previous knee injuries helps our doctors to make an accurate diagnosis and recommend appropriate treatment.

Diagnostic Imaging

NYU Langone radiologists, who specialize in administering and interpreting diagnostic imaging tests, work closely with orthopedic doctors to take detailed images of the knee.

X-ray

X-ray images can reveal the location of a patella fracture. They also help your doctor to determine whether the break goes all the way through the bone or just affects the surface.

CT Scan

During a CT scan, a series of X-rays are taken to create two- or three-dimensional pictures of the knee, letting doctors examine a patella fracture from many different angles. Your doctor may recommend a CT scan if an X-ray reveals that a fracture has occurred in more than one place on the patella or if pieces of bone have separated from the patella and moved to different parts of the knee.

NYU Langone specialists use new radiology techniques to ensure that CT scans have the lowest possible dose of radiation.

MRI Scan

If a patella fracture is severe and bone fragments have affected ligaments, tendons, or nerves, doctors may recommend MRI. An MRI scan uses magnetic fields to take detailed images of the soft tissue surrounding the knee and can reveal if there are torn or strained ligaments or tendons, or if a bone fragment is pressing on a nearby nerve. If soft tissue is damaged, doctors may recommend immediate surgery.

Bone Scan

Your doctor may recommend a bone scan if pain and swelling suggest a fractured patella and additional imaging is needed, but an MRI cannot be used because you have a pacemaker or other implanted metal device. However, this is rare.

First, a technician injects a small amount of dye into a vein in your arm. This dye, called a tracer, travels through the bloodstream and accumulates in places where your cells and tissues are most actively working to make repairs.

After the tracer has had one or two hours to move through the bloodstream, a radiologist scans your body using a special camera designed to capture images of the tracer. If it accumulates in certain places more than others, this may indicate the presence of an injury.