How Common is Patella Fractures?

Patella fractures make up around 1% of all broken bones.

What are signs and symptoms of Patella Fractures?

Signs and symptoms of Patella Fractures include: - Widespread pain in the knee - Tenderness around the knee - Fluid buildup in the knee joint - Weakness in the knee - Instability of the knee - Difficulty with stairs In addition, when examining the injured knee, doctors may also look for the following signs: - Damage to the soft tissues around the knee - Grinding of bone on bone when touching the knee - A gap where the fracture is located - Swelling due to bleeding into the joint It is important to note that fractures of the kneecap that occur around a joint replacement may not look or feel the same as breaks in a natural kneecap. Some patients may not remember any specific event that could have caused their fracture, and initially, some patients may have minimal or no symptoms at all.

How do you get Patella Fractures?

Patella fractures can be caused by either a direct hit or an indirect force, with the type of force often shaping the fracture itself. The kneecap usually breaks due to indirect tension, when forces from the parts of the leg that help extend, like the quadriceps, become too strong for the bone to manage. These indirect injuries are often caused by things like a fall or a hard hit to the front of the knee in a car accident, due to the kneecap's location near the surface of the skin.

What else can Patella Fractures be?

When diagnosing Patella Fractures, a doctor needs to rule out the following conditions: 1. Knee issues: Doctors need to rule out any other knee-related issues that may be causing the symptoms. 2. Bipartite patella: In cases where the kneecap remains as two separate bones instead of fusing together, doctors need to differentiate between bipartite patella and fresh fractures. 3. Fractures around a knee prosthetic: If a fracture is suspected around a knee prosthetic, doctors need to use formal anteroposterior, lateral, and 'skyline' radiographs, as well as a Technetium-99m bone scan if necessary, to identify hidden fractures or differentiate between new or old fractures.

What kinds of test are needed for Patella Fractures?

The types of tests that are needed for patella fractures include: - Detailed knee images taken from the front-to-back (anteroposterior, or AP) and side (lateral) angles - Imaging for a bipartite patella, which shows a fragment at the upper outside corner of the patella - Formal anteroposterior, lateral, and 'skyline' radiographs for suspected fractures around a knee prosthetic - In rare cases, a Technetium-99m bone scan may be used to identify hidden fractures or differentiate between new or old fractures

How is Patella Fractures treated?

Patella fractures can be treated through nonsurgical or surgical methods. Nonsurgical treatment is suitable for small fractures with minimal displacement or movement, where the muscles are still intact. This may involve wearing a leg splint, knee brace, or other support to stabilize the fracture while gradually returning to weight-bearing activities. Physical therapy is also important to regain full range of motion and strengthen the knee. Surgical intervention is necessary for major displacements, fractures that interrupt muscular functions, and open fractures. Surgical techniques such as tension band wire fixation or the Modified Anterior Tension Band (MATB) technique may be used, and additional reinforcement may be required for complex fractures. In some cases, partial or complete removal of the kneecap may be necessary, but this can reduce the efficiency of the quadriceps. After surgery, treatment is similar to nonsurgical care, with the use of a knee brace and gradual movement of the knee to prevent stiffness.

What are the side effects when treating Patella Fractures?

The side effects when treating Patella Fractures can include: - Issues with surgical hardware, such as symptoms from the hardware used during surgery, device failure, and wire moving away from its intended position. - Knee stiffness. - Infections and non-healing fractures, which are more likely with open fractures. - Bone tissue death in the kneecap, although this does not usually impact the overall success of treatment. - Complications specific to Type I, Type II, and Type III periprosthetic fractures, including non-healing fractures, joint stiffness, loosening of the patellar button, failure of fixation, extensor lag, nonunion, infection, instability, and the need for revision surgery.

Patella Fractures

What is Patella Fractures?

The patella, or kneecap, is the largest floating bone in our bodies. It has a thick layer of cartilage on its backside, making it the part of the body with the thickest cartilage. The patella is split into two parts, the medial and lateral facets, by a vertical ridge and it connects with the femur, or thigh bone.

The kneecap serves several purpose: It protects the front of the knee joint, it’s the attachment point for a tendon of the quadriceps muscle (used for straightening the leg), and it also acts like a lever to help this muscle work more efficiently. The bottom of the kneecap is connected to the patella tendon. The patellar retinaculum, a band of tissue that helps give the kneecap its shape and secure its position, is made up from parts of different muscles and the fascia lata, a layer of tissue located on the thigh.

Your kneecap gets its blood supply from the geniculate arteries. The upper blood vessels are found in front of the quadriceps tendon and the lower ones pass behind the patellar tendon. But the key blood supplier for the kneecap comes from the lower part of it through a storage of fat located below the kneecap.

What Causes Patella Fractures?

Patella fractures, or broken knee caps, can be caused by direct hits or indirect pressure, and the type of injury often affects the fracture pattern. The most common reason the patella break is indirect pressure that feels like tension. This could happen if the forces produced by the knee-extension mechanism become too much for the bone’s mechanical qualities to handle. Since the patella is located just under the skin, a direct injury might happen if the front of the knee gets a hard hit, like from a fall or an impact from a car dashboard during an accident.

As the demand for primary total knee replacements is projected to grow significantly – expected to reach 3.48 million procedures in 2030 (which is an increase of 673% from 2005), there is also expected to be an increase in patella fractures around artificial knee joints. This rise is due to a combination of increasing life expectancy, people being more active, and more people needing total knee replacements, which in turn has also led to an increase in these artificial-joint-related fractures.

These fractures around artificial joints, known as periprosthetic fractures, are complex problems. They require a detailed patient history, extensive discussions with the patient and their family to understand the upcoming procedure, and in-depth surgery planning. These fractures can also be caused by a direct hit or excessive load on the patella or quadriceps tendon, similar to fractures on the natural patella.

Risk Factors and Frequency for Patella Fractures

Patella or kneecap fractures make up about 1% of all bone fractures and are more often seen in men. Some patella fractures (6% to 9%) are open injuries, which usually happen along with other injuries due to high impact. In some people, a part of the patella, typically the top outside edge, doesn’t fuse completely. This results in a bipartite patella, which can sometimes be mistaken for a fracture on X-rays. About half of people with a bipartite patella have it in both knees.

Fractures of the patella that happen around artificial knee joints, known as periprosthetic fractures, are serious injuries and the most common problem after total knee replacement surgery. A large study of 12,000 knee replacements found these fractures occurred in 0.68% of cases. They’re more common after the surgery than during it. Knee replacements that require a second surgery have double the risk of these fractures after the operation (1.8%) and nine times during the operation (0.2%) compared to the initial knee replacement. Periprosthetic fractures are grouped according to when they occur (during or after surgery) and further classified by the extent of the displacement, the condition of the bone tissue, and the stability of the kneecap and muscle that extends the knee.

Signs and Symptoms of Patella Fractures

The first steps to identifying an injury involve a detailed review of your medical history and a physical examination. This will help to understand how the injury was caused and to identify any other possible injuries. Some patients, for instance, might have injuries to the hip socket or lower leg if they had an accident involving a high-impact dash. When looking at an injured knee, doctors are mainly concerned with any damage to the soft tissues surrounding the joint.

In some cases, if an open knee wound is suspected, a saline load test might be done, where 155 to 175 mL of sterilized saline solution is used. A physical touch test on unopened injuries can provide clues such as a grainy sound or feeling, a gap where the fracture is, or swelling that might indicate internal bleeding within the joint. Doctors also do a straight leg test to check the muscle that extends the leg, but this test can sometimes be hindered by the patient’s pain.

Fractures of the kneecap around a prosthesis don’t usually present the same way as fractures of a healthy kneecap. Trauma or injury is often the cause of these types of fractures around a prosthesis, but some patients may not even remember a specific incident that led to the fracture. Surprisingly, about 44% of patients with this type of fracture without a known cause report minimal or no symptoms at all. However, similar to fractures of a normal kneecap, traumatic injuries might cause symptoms like:

Spread out pain in the front of the knee
Tenderness to the touch
Swelling
Weakness
Instability
Difficulty with climbing stairs

Testing for Patella Fractures

If your doctor suspects you have a knee issue, such as a patellar fracture, they may use specific x-rays taken from the front (anteroposterior or AP) and side (lateral) of your knee. These pictures help your doctor check if the pieces of your kneecap are out of place. Even though it’s rare, more advanced imaging may sometimes be used for more complicated kneecap fractures.

There’s also a condition known as bipartite patella, where the kneecap (or patella) is made up of two parts instead of one. This usually shows up as a separate piece at the upper outside corner of the kneecap. It doesn’t mean you have a fracture; in fact, you can tell it’s different because the edges around this piece will look smooth. Interestingly, if one knee has a bipartite patella, there’s a 50% chance the other knee will have it too.

If you have an artificial kneecap (known as a ‘prosthetic’) and your doctor thinks you may have a fracture in it, they will again use x-rays taken from different angles to examine it. In rare cases, they may use a special type of scan called a Technetium-99m bone scan. This can help them see hidden fractures or tell if the fracture is new or old. However, this scan must be analyzed carefully because it may show positive results up to four years after an initial knee injury.

Treatment Options for Patella Fractures

The main goal in treating fractures in the kneecap (or patellar fractures) is to restore the knee’s ability to straighten. Sometimes, this can be done without surgery. This might be the case for fractures that are barely displaced (meaning the pieces of broken bone haven’t moved far apart). The decision may also depend on the patient’s overall health or mental state, which might make surgery risky.

Fractures are usually stabilized using a long-leg splint, a device that immobilizes the knee, or a special knee brace. Within a week or so, the patient might begin moving the knee gently, to prevent stiffness and to start rebuilding strength. A physical therapist can guide these exercises. Doctors will take new x-rays to make sure the fracture isn’t getting worse. About six weeks after the injury, the patient can start doing exercises to add resistance and build more strength.

Surgery may be required for more serious fractures, or if the knee has lost its ability to straighten. The standard surgical technique, developed by the AO (Association for the Study of Internal Fixation), uses wire to hold the broken pieces of bone together. This technique relies on having a clean, straight split in the bone. Else, various modifications exist to deal with different types of fractures. Some use different materials or less invasive techniques. Several of these techniques still share the goal of holding the broken pieces of bone together while the body heals.

Despite the many ways to approach these fractures, healing rates are typically high with surgery, and most patients have good outcomes. That being said, the goal is always preservation of the kneecap. But in some cases, resection — or removal — of all or part of the kneecap may be necessary. The effect of this surgery on the strength of the knee should be discussed with the doctor.

After surgery, similar strategies are used as with non-surgical treatment. The patient’s knee will be immobilized in a brace, and they may start exercises as soon as pain allows. A physical therapist will guide these exercises to prevent stiffness and build strength. The timing of exercises can be adjusted depending on the type and seriousness of the fracture.

Finally, fractures in artificial kneecaps (periprosthetic fractures) can be tricky to treat. Specialists familiar with the various options for treatment should handle these cases. Many variables, including the type and severity of the fracture, can impact the treatment plan.

Possible Complications When Diagnosed with Patella Fractures

After surgery, patients may experience complications such as problems with the surgical hardware, failure of the implanted device, or migration of the surgical wire, along with stiffness in the knee. Infections and non-healing of fractures are less common but occur more frequently in open fractures. One possible but less common issue is the death of bone in the kneecap, which has been reported in up to 25% of cases. However, this doesn’t usually affect the overall outcome.

When looking at specific types of fractures around a prosthetic joint (periprosthetic fractures), complications show up differently. In the case of Type I fractures, 18% of patients developed complications like a fracture not healing, joint fibrosis (a condition where excess fibrous connective tissue develops in an organ), and loosening of the patellar button. Type II fractures had a higher complication rate at 50%, with almost half of these patients needing another surgical procedure due to instability, pain, and weakness. Type III fractures carried an even higher risk of complications at 66%. The most common issues were failure of the fixation (the surgical process to stabilize the fracture), non-healing of the fracture, infection, joint instability, and fibrosis. A quarter of these patients had to have another surgery.

Potential Complications: