Understanding Patellar Fractures: Causes, Symptoms, and Treatment Options

A patellar fracture refers to a break in the patella, commonly known as the kneecap. This small yet vital bone is positioned at the front of the knee and serves as a protective shield for the knee joint. Due to its role, the patella is particularly susceptible to fractures caused by:

• Direct falls onto the knee
• High-impact trauma, such as a football tackle where a helmet strikes the kneecap or a high-speed impact from a baseball or softball
• Collision injuries, such as hitting the dashboard with the kneecap during a car accident

Patellar fractures are significant injuries that may hinder the ability to straighten the knee or walk. Treatment for Patellar Fractures:

• Non-Surgical: Simple fractures, where the bone remains in alignment, can often be managed with a cast or splint, allowing the bone to heal naturally over time.
• Surgical: For more complex fractures, where the bone fragments are displaced, surgical intervention is typically required. This procedure realigns and stabilizes the kneecap, ensuring proper healing and the restoration of knee function.

Timely medical evaluation and treatment are essential to achieve the best outcomes and prevent long-term complications.

The patella covers and protects the knee joint.

 

Description of Patellar Fractures

Patellar fractures can present in a variety of patterns. The break may be a clean, straightforward split into two pieces or a more severe injury where the kneecap shatters into multiple fragments. These fractures can occur at different locations on the patella, such as the upper, middle, or lower sections. In some cases, multiple fractures can occur simultaneously, affecting more than one area of the kneecap. Understanding the type and location of a patellar fracture is essential for determining the most effective treatment approach.  

This X-ray of a knee taken from the side shows a patella that has been fractured in three places.

Stable Fracture

A stable patellar fracture is a type of nondisplaced fracture, meaning the broken bone pieces remain largely aligned. The fragments may either stay in contact or have a minimal separation of just one or two millimeters. In this type of fracture, the stability of the bone ensures that it remains in proper alignment throughout the healing process, often requiring less invasive treatment methods. Stable fractures typically respond well to conservative management, such as immobilization with a cast or splint, allowing the natural healing process to restore the bone's integrity.

Illustration and X-ray show a vertical, stable fracture of the patella.

Displaced Fracture

A displaced patellar fracture occurs when the broken ends of the bone are misaligned and separated. This misalignment disrupts the normally smooth surface of the knee joint, potentially impairing its functionality and causing pain during movement. Due to the severity of this fracture type, surgical intervention is often required to realign the bone fragments and restore the joint's normal structure. This ensures proper healing and helps prevent long-term complications, such as joint stiffness or arthritis.  

Illustration and X-ray show a front (left) and side (right) view of a two-part fracture across the patella (transverse fracture) with slight displacement between the broken pieces of bone.

Comminuted Fracture

A comminuted fracture occurs when the patella breaks into three or more fragments. The stability of this type of fracture depends on its specific pattern. It may be classified as either stable, where the bone fragments remain aligned, or unstable, where the pieces are misaligned and require surgical intervention.

Open Fracture

An open fracture is a severe injury where the broken bone protrudes through the skin or a wound penetrates down to the bone. This type of fracture often causes extensive damage to the surrounding soft tissues and requires a longer healing time due to its complexity. Open fractures are particularly dangerous because the broken skin increases the risk of infection in both the wound and the exposed bone. Immediate medical attention is crucial to clean the wound, prevent infection, and initiate appropriate treatment to promote healing and minimize complications.

A comminuted fracture

Causes of Patellar Fractures

Patellar fractures typically result from direct or indirect trauma to the knee. Common causes include: Direct Impact: Falling directly onto the knee or sustaining a sharp blow, such as in a head-on car collision where the kneecap strikes the dashboard. Indirect Trauma: Sudden, forceful contraction of the quadriceps muscle can indirectly fracture the patella by pulling it apart.

Symptoms of Patellar Fractures

The most recognizable symptoms of a patellar fracture include: Pain and Swelling: Localized in the front of the knee. Bruising: May occur around the knee joint. Movement Impairment: Inability to straighten the knee, perform a straight leg raise, or maintain knee extension. Weight-Bearing Issues: Difficulty or inability to stand or walk.

Doctor Examination and Diagnosis

Physical Examination

Your doctor will begin by reviewing your symptoms and medical history, followed by a thorough examination of the knee. Key aspects include: Fracture Detection: The edges of the fracture are often palpable through the skin, especially in displaced fractures. Checking for Hemarthrosis: This condition involves the collection of blood in the joint space due to the fracture, leading to significant swelling. If needed, your doctor may perform a procedure to drain the blood and alleviate pain.

Imaging Tests

To confirm the diagnosis and assess the fracture's severity, X-rays are typically ordered. These images provide detailed information about the fracture pattern and help guide the treatment plan. Early diagnosis and treatment are critical to managing patellar fractures effectively and ensuring optimal recovery.  

The significant displacement of this patient's fracture has created a large gap between the pieces of bone.

 

X-Rays: An Essential Tool for Diagnosing Patellar Fractures

X-rays are a vital imaging technique used to visualize dense structures like bones. When diagnosing a patellar fracture, your doctor will order X-rays from multiple angles to assess the break and evaluate the alignment of the bone fragments.

Identifying Bipartite Patella

In rare cases, a person may have a congenital condition known as bipartite patella, where the patella consists of two or more separate bone pieces that did not fuse together during development. This condition can sometimes be mistaken for a fracture on an X-ray. To differentiate between a fracture and a bipartite patella, your doctor may: Examine the X-ray images for characteristic signs of bipartite patella. Take an X-ray of the opposite knee, as many individuals with bipartite patella have the condition in both knees. By carefully analyzing the X-rays, your doctor can ensure an accurate diagnosis and tailor the treatment approach accordingly.  

This X-ray of a patellar fracture shows significant displacement between the broken pieces of bone.

 

Nonsurgical Treatment

In cases where the broken bone fragments are not displaced, surgery may not be necessary. Instead, your doctor may use a cast or splint to immobilize the knee, keeping it straight to prevent movement. This approach ensures that the bone fragments remain properly aligned during the healing process. Weight-Bearing Restrictions: Depending on the type of fracture, your doctor may allow partial weight-bearing on the affected leg while wearing the cast or brace. However, with certain fractures, weight-bearing may be prohibited for 6 to 8 weeks. Your doctor will provide detailed instructions based on your condition.

Surgical Treatment

If the bone fragments are displaced, surgical intervention is usually required to realign and stabilize the patella. Displaced fractures often struggle to heal naturally, as the strong quadriceps muscles attached to the patella can pull the fragments apart during the healing process.

Timing of Surgery

Closed Fractures: If the skin remains intact, surgery may be delayed until any abrasions or scrapes around the knee have healed. Open Fractures: If the fracture pierces the skin, immediate surgery is necessary to minimize the risk of infection. The wound and bone are thoroughly cleaned, and the fracture is typically repaired during the same surgical procedure. Surgical Procedures The type of surgery performed depends on the nature and severity of the fracture.

Transverse Fracture Repair

For fractures that split the patella into two parts, surgeons often use screws or a combination of pins and wires arranged in a figure-of-eight tension band. This technique compresses the two fragments together, promoting healing. This method is most effective for fractures near the center of the patella but is less suitable for fractures at the ends or comminuted fractures (those with multiple pieces), as over-compression can occur.

Alternative Fixation Methods

Small screws or a combination of screws and plates may be used as an alternative, particularly for fractures that cannot be stabilized effectively with a tension band. Your doctor will discuss the most appropriate surgical approach for your specific fracture, along with any potential risks or complications associated with the procedure. Early and effective treatment is crucial for restoring knee function and minimizing long-term issues.

In this illustration and X-ray, a figure-of-eight tension band has been used to hold a transverse fracture together.

Comminuted Fracture

A comminuted fracture occurs when the patella breaks into multiple fragments. This is most common at the bottom of the kneecap and often results from the patella being first pulled apart and then crushed during a fall. Small Fragment Removal: In cases where the bone fragments are too small to reattach, your doctor may remove them. The patellar tendon is then reattached to the remaining part of the kneecap to restore function. Center Fractures: If the fracture is at the center of the kneecap with multiple separated pieces, a combination of wires and screws may be used to stabilize the fragments. Severe Cases: When reconstruction is not feasible, small, irreparable portions of the kneecap may be removed. Complete removal of the patella is considered only as a last resort.

Recovery After a Patellar Fracture Pain Management

Most patellar fractures cause moderate pain for a few days to weeks. Effective pain relief methods include: Ice Application: Reduces swelling and discomfort. Elevation: Keeps the affected leg elevated to minimize swelling. Over-the-Counter Pain Relievers: Non-prescription medications like acetaminophen or ibuprofen are often sufficient. Prescription Medications: In cases of severe pain, your doctor may prescribe stronger painkillers for short-term use.

Rehabilitation

Rehabilitation is a critical component of recovery for both surgical and nonsurgical treatments. Extended immobilization in a cast or splint can lead to stiffness and muscle weakness. A physical therapist will guide you through exercises to: Improve range of motion in the knee. Strengthen weakened leg muscles. Reduce joint stiffness.

Weight-Bearing

Your doctor will advise when and how to begin weight-bearing activities. Initially, this may involve gently touching your toe to the floor. As healing progresses and muscles regain strength, you can gradually increase the weight on your leg.

Potential Complications of Patellar Fractures Posttraumatic Arthritis

This form of arthritis can develop even when the fracture heals correctly, due to damage to the articular cartilage. Symptoms include joint pain and stiffness, with severe arthritis occurring in a small percentage of cases. Milder forms, such as chondromalacia patella (softening of cartilage), are more common.

Muscle Weakness

Persistent weakness in the quadriceps muscle and reduced knee motion, including difficulty with extension and flexion, can occur. While not typically disabling, these effects may be long-lasting. Chronic Pain Long-term pain in the front of the knee is common and may be linked to arthritis, stiffness, or muscle weakness. Some patients find relief with the use of knee braces or supports.

Expected Outcome

Recovery time varies depending on the severity of the fracture, the type of treatment, and the duration of rehabilitation. Most patients return to normal activities within 3 to 6 months, though severe fractures may require more time. To protect your knee and reduce the risk of future problems, your doctor may recommend: Avoiding repetitive deep knee bending or squatting. Limiting activities like climbing stairs, using ladders, or walking on steep inclines. With proper care and adherence to rehabilitation, many patients achieve excellent outcomes after a patellar fracture.