Patella Fractures

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A patella fracture is an injury to the kneecap. The kneecap is one of three bones that make up the knee joint. The patella is coated with cartilage on its undersurface and is important in providing the strength of extension (straightening) of the knee joint.

Common Symptoms of Patella Fracture
Verywell / Gary Ferster

Causes of a Patella Fracture

A patella fracture most often occurs from a fall directly onto the kneecap. When the fracture occurs due to this type of direct trauma, there is often damage to the overlying skin, and because of the limited amount of soft tissue, this can easily become an open fracture. Patella fractures can also occur when the quadriceps muscle is contracting but the knee joint is straightening (a so-called "eccentric contraction"). When the muscle pulls forcefully in this manner, the patella can fracture.

There are certain situations when the kneecap may fracture even with minor injuries. Sometimes these injuries are pathologic fractures—bone fractures that occur as a result of weak bone. Pathologic fractures can be caused by osteoporosis (thin bone), bone infection, or tumors.

Signs of a Patella Fracture

Patella fractures can cause severe pain and difficulty walking. Some of the more common symptoms of this injury include:

Pain: Patella fractures are generally quite uncomfortable. Keeping the knee straight can help significantly with discomfort, and bending the joint is typically very painful.

Swelling: Swelling and bruising around the front of the knee is typical of a patella fracture. Often, as days go by, the swelling extends down the leg and even into the foot. It is not uncommon for the bruising to also extend into the calf and foot over several days.

Inability to Lift Foot: The most common test to diagnose this injury is called a straight leg raise test. This test finding may be present with other injuries but can help determine when treatment is necessary.

A Palpable Defect in the Kneecap: Often the damage to the kneecap can be felt through the skin. The ability to feel the patella fracture is easiest soon after the injury before swelling has become more significant.

Patella Fracture Treatment

Patella fractures should be seen in the emergency room. X-rays will determine the type of fracture and the amount of displacement (separation) of the fracture. One of the critical factors in determining treatment is a thorough examination. Specifically, doctors will check if the patient can perform a straight leg raise.

A straight leg raise test is done by having the patient lie flat on a bed. With the leg straight, the patient should then raise his or her foot off the bed and hold it in the air. This tests the function of the quadriceps muscle and its attachment to the shin bone (tibia). A disruption of the quadriceps tendon, patella or patellar tendon can lead to the inability to perform a straight leg raise. If a straight leg raise can be done, then non-operative treatment may be possible in the setting of a patella fracture.

One of the common symptoms of a patella fracture is knee swelling. The swelling is caused by bleeding from the fractured bone ends into the knee joint. Patients with a large amount of blood in the knee may benefit from draining the blood for pain relief. Immobilizing the knee with a knee brace will also help minimize discomfort.

Patella Fracture Surgery

Patients with nondisplaced (not separated) or minimally displaced fractures who can perform a straight leg raise (as described above) can usually be treated without surgery. A long leg cast or a knee immobilizer can be used for the treatment of these types of patellar fractures.

When surgery is necessary, an incision is made over the front of the knee joint. The fractured ends of the bone are realigned and held in place with some combination of pins, screws, and wires. In some cases, a portion of the patella can simply be removed, but this is usually done for smaller fracture fragments.

Rehab after Surgery

Following surgery, patients will need to keep their knee in a straight position to allow for initial healing. Exactly when the knee can begin moving depends on the strength of the repair your surgeon is able to achieve. Gentle motion can usually begin in the first weeks following surgery. In situations where the bones are held solidly, the early motion of the knee helps to achieve the best results after surgery.

The most common complication of patella fracture surgery is that the metal implants can be painful over time—especially when kneeling. Because of this, it is not uncommon for a second procedure to remove the metal implants. This procedure is usually done at least a year after the initial surgery.

Other possible complications include:

  • Infection
  • Non-healing fractures
  • Failure of the fixation to hold the fragments in place
  • Kneecap pain (chondromalacia)
  • Knee arthritis

One of the important aspects of surgery is to realign the cartilage surface of the kneecap to prevent the development of arthritis of the knee joint. Because of damage to the knee joint cartilage when a fracture occurs, there is a higher chance of the development of arthritis of the joint. If kneecap arthritis becomes severe, some people may ultimately need a knee replacement or a partial knee replacement of the kneecap.

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