All You Need To Know About Patellar (Knee) Fractures

A patellar fracture is a break in the patella, commonly referred to as kneecap, the small bone that sits at the front of the knee. As the patella acts as a shield for the knee joint, it is vulnerable to fracture. A fracture can happen if one falls directly onto the knee or hits it against the dashboard in a vehicle collision. Patellar fractures are serious injuries that can make it very hard or even impossible to walk or straighten the knee.

Certain simple patellar fractures can be treated by wearing a splint or cast until the bone is healed. However, in most cases, the pieces of bone get displaced during the injury. To treat these more complex patellar fractures, surgery is required to restore and stabilise the kneecap and allow for the knee to be able to function again.

Which part of the leg does it concern?

The patella is a small bone located in front of the knee joint, where the femur (thighbone) and tibia (shinbone) meet. It covers and protects the knee and connects the muscles in the front of the thigh to the tibia.

A smooth substance called articular cartilage covers the ends of the femur and the undersides of the patella. This cartilage helps the bones glide easily along one another as the knee moves.

What kinds of patellar fractures are there?

The patella can be fractured in numerous ways. Fractures can range from a simple two-piece break to one where the bone is broken into many pieces.

A break can occur at the top, centre or lower part of the bone. At times, fractures can even occur in more than one area of the kneecap.


The different kinds of patellar fractures

Stable fracture
Stable fractures are nondisplaced. In this kind of fracture, the pieces of bone may remain in contact with one another or be separated by one or two millimetres. The bones also normally stay in position during the healing process.

Displaced fracture
In a displaced fracture, the broken ends of the bone are separated and do not align correctly. In addition, the usually smooth joint surface may also be disrupted. Displaced fractures normally require surgery to place the pieces of bone back together.

Comminuted fracture
The bone is shattered into three or more pieces in a comminuted fracture. Comminuted fractures may either be stable or unstable, depending on the specific pattern of the fracture.

Open fracture
In an open fracture, the bone is broken in such a way that the bone fragments stick out through the skin or a wound is penetrated down to the bone. This kind of fracture may take a longer time to heal and usually involves damage to the surrounding soft tissues.

Since the skin is broken, there is a greater risk of infection in both the wound and bone. This makes open fractures especially serious, and immediate treatment is necessary to prevent infection.

What causes patellar fractures?

Typically, patellar fractures are caused by:

  • Receiving a sharp blow to the knee, like hitting the knee on the dashboard during a head-on vehicle collision
  • Falling directly on the knee

On top of that, the patella can be fractured indirectly. For example, a sudden contraction of the quadriceps muscle in the knee can pull the patella apart.


What are the symptoms of a patellar fracture?

The symptoms of a patellar fracture may include:

  • Severe pain around the kneecap area
  • Swelling
  • Bruising
  • Tenderness when the kneecap is pressed
  • Not being able to walk
  • Difficulty in keeping the knee straight or extended in a raise
  • A deformed appearance of the knee because of the fractured pieces


How is a doctor evaluation carried out?

Physical examination

First, the doctor will discuss the patient’s symptoms and medical history. Next, the knee will be examined. The edges of a fracture can usually be felt through the skin, especially if the fracture is displaced.

During the examination, the doctor will check for hemarthrosis. Hemarthrosis is a condition where blood from the fractured bone ends accumulates inside the joint space, causing painful swelling. The doctor may drain the blood in the knee to relieve pain if there is a large amount of blood.

X-ray tests will also be performed to help diagnose the fracture.



X-rays can provide images of dense structures like bone. A number of X-rays from different angles will be performed. This is to help the doctor look for a fracture and view the alignment of the bones.

Once in awhile, a person may be born with extra bones in the patella that have not grown together. This is known as bipartite patella, and can be mistaken for a fracture. X-rays are able to identify this condition. Since a number of people have bipartite patella, an x-ray may be taken of both knees.

How are patellar fractures treated?

Nonsurgical Treatment

One may not require surgery if the pieces of bone are not displaced from their rightful position. A cast or splint may be applied to keep the knee straight and prevent motion in the leg.  This will ensure the broken ends of bone are kept in the correct position while they heal.

Depending on the specific fracture, weight may be allowed to be put on the leg with a cast or brace. However, weight bearing is prohibited for 6 to 8 weeks with certain fractures. A doctor will explain more about the restrictions on weight bearing to each patient.


Surgical treatment

Surgery will likely be required if the pieces of bone are displaced. Fractured patellar bones that are not close together will often have difficulty healing. Furthermore, the strong thigh muscles that attach to the top of the patella can pull the broken pieces out of place during healing.

Considering the skin around the fracture has not been broken, the doctor may recommend waiting for any abrasions to heal before going for surgery.

Open fractures, on the other hand, have a higher risk of infection and are typically scheduled for surgery within hours. During the procedure, the cuts from the injury and surfaces of the bone are thoroughly cleaned out. The bone will then usually be repaired during the same procedure.


Surgical procedures

The kind of surgery that is performed usually depends on the type of fracture. Before the procedure, the doctor will discuss the procedure and any potential complications with the patient.

Transverse fracture
These two-part fractures are typically fixed in position using screws or pins and wires, along with a “figure of eight” configuration tension band. This band presses the two pieces of broken bone together.

This method works best for treating fractures near the centre of the patella. However, it will not work well for fracture pieces at the ends of the kneecap as the pieces are too small for this procedure. Breaks that are in numerous pieces may also be overcompressed by this tension band.

Alternatively, small screws and small plates may be used to secure the bones in a transverse fracture.

Comminuted fracture
In a comminuted fracture, the top, or more typically the bottom of the patella is broken into several small fragments. This kind of fracture occurs when the kneecap is first pulled apart from the injury, then crushed when the patient falls on it. Because the bone fragments are too tiny to fix back into place, they will be removed. 

If the kneecap is broken into many separated pieces at the centre, a combination of screws and wires may be used to fix it. Alternatively, small fragments of the kneecap that cannot be reconstructed may be removed. This can also produce good results. Lastly, a complete removal of the kneecap is done as a last option.

What does the recovery process of a patellar fracture look like?

Pain management

It is normal for fractures to hurt moderately for a few days to weeks. Simple pain relief methods such as icing, elevating the leg and taking non-prescription medications have been found to be effective.

For pain that is more severe, prescription-strength medication such as opioids may be prescribed for a few days.

Although opioids can help to relieve pain post-surgery, one should be careful as opioid dependency and overdose is a major public health concern. As such, opioids are usually prescribed for only a short amount of time. It is crucial to use opioids only as instructed by a doctor. One should stop all use of opioids once the pain begins to improve.


How is the rehabilitation process for a patellar fracture like?

For both surgical and nonsurgical treatment, rehabilitation plays a crucial role in getting a patient back to their everyday routines.

The knee may become stiff and the thigh muscles weak after keeping the leg immobilised in a cast for a long period of time.

During rehabilitation, specific exercises will be taught to help decrease stiffness, strengthen the leg muscles and improve the range of motion in the knee.



Patients will be instructed as to when they can begin bearing weight on the leg. Initial weight-bearing exercises are normally limited to gently touching the toe to the floor. One will be able to bear more weight on the leg as the injury heals and the muscles strengthen.


What are the possible complications of a patellar fracture?

It is possible for some patients to experience long-term complications even after successful treatment.

Posttraumatic arthritis

Posttraumatic arthritis is a form of arthritis that develops after an injury. Even when the bones heal normally, the articular cartilage can be damaged, causing stiffness and pain over time. Only a small fraction of patients with patellar fractures develop severe arthritis. However, chondromalacia patella, mild to moderate arthritis, is much more common.

Muscle weakness

After a fracture, some patients may experience permanent weakness of the quadriceps muscle in the front of the thigh. Some loss of motion in the knee, including both straightening (extension) and bending (flexion), is also common. However, this loss of motion is typically not disabling.

Chronic pain

It is common to experience long-term pain in the front of the knee with patellar fractures. Although the cause of this pain is not fully known, it is possibly related to stiffness, muscle weakness and posttraumatic arthritis. Certain patients may find more comfort in wearing a support or knee brace.

What are the outcomes of a patellar fracture?

The speed of recovery from a patellar fracture is dependent on a few factors, such as the severity of injury and the time needed for rehabilitation. Whether the treatment was a surgical or nonsurgical one also plays a part.

Majority of patients are able to resume their daily activities within 3 to 6 months. This period may take longer for patients with severe fractures.

Certain lifestyle changes may be suggested to help protect the knee and prevent future problems. For example, activities that involve repetitive deep knee bending or squatting should be avoided. This includes climbing the stairs or ladders.