Patella Fracture: Symptoms, Types, Causes and Treatment

Patella fractures, though accounting for only about 1% of all skeletal injuries, can have a profound effect on knee function and mobility. As the kneecap plays a crucial role in the extensor mechanism of the leg, any disruption can lead to pain, weakness, and significant limitations in daily activities. Understanding the symptoms, fracture types, causes, and modern treatment options is key to achieving the best outcomes for patients and guiding informed decisions throughout the recovery journey.

Symptoms of Patella Fracture

When a patella fracture occurs, the symptoms are often dramatic and can severely impact a person's ability to move or bear weight. Recognizing these signs early can help ensure prompt diagnosis and treatment, minimizing the risk of long-term complications.

Major Signs	Onset	Functional Impact	Sources
Acute pain	Immediate	Limits knee movement	1 6 9 10
Swelling	Rapid	Causes knee stiffness	1 6 9
Bruising	Within hours	Discomfort, visual clue	6 9
Inability to extend knee	Immediate	Loss of active straight-leg raise	1 6 9 10
Palpable gap or deformity	Immediate	Visible/feelable defect	1 6
Difficulty walking	Immediate	May require assistive device	9 10

Table 1: Key Symptoms

Breaking Down the Symptoms

Pain and Swelling

• Acute pain is the hallmark, usually centered at the front of the knee and worsened by movement or touching the area.
• Swelling develops quickly due to bleeding within the joint (hemarthrosis), often accompanied by warmth and tenderness 1 6 9.

Bruising and Physical Changes

• Bruising (ecchymosis) can appear over the patella within hours. In some cases, the skin may look stretched or shiny from swelling 6 9.
• You might feel or see a gap or irregularity over the kneecap if the fracture fragments are displaced 1 6.

Loss of Function

• One of the most significant signs is difficulty or inability to straighten the knee or lift the leg when lying down. This occurs if the extensor mechanism is disrupted 1 6 9 10.
• Walking is often impossible or severely limited; patients may need crutches or other support 9 10.

Longer-Term Issues

• Even after initial healing, patients can experience:
  • Knee pain with activity
  • Difficulty climbing stairs or kneeling
  • Persistent weakness in the quadriceps muscle 10

Special Note: Children

• In children, symptoms may be less obvious, and special types of fractures (like sleeve fractures) can be easily missed. Swelling and inability to extend the knee may be the only signs 7.

Types of Patella Fracture

Patella fractures are not all the same; they vary widely in pattern and complexity. Recognizing the type of fracture is essential for guiding treatment and predicting outcomes.

Type	Description	Common Features	Sources
Transverse	Horizontal break across patella	Most common, often 2-part	1 2 3 6 9
Vertical	Vertical/longitudinal split	Less common, stable if undisplaced	2 5 9
Comminuted	Multiple fragments	Complex, often from high-energy trauma	1 3 9
Pole (avulsion)	Fragment at upper/lower pole	May disrupt tendon, often in children	1 7 9
Stellate	Star-shaped, radiating lines	Typically from direct impact	3
Sleeve (children)	Cartilage/periosteum pulled off	Unique to children, hard to see on X-ray	7

Table 2: Patella Fracture Types

Understanding the Fracture Types

Transverse Fractures

• The most frequent, accounting for over half of adult patella fractures 1 2.
• Usually caused by indirect forces (sudden muscle contraction).
• Can be displaced or non-displaced; displacement often requires surgery 1 2 6.

Vertical Fractures

• Represent about 12-17% of cases 2 5.
• Typically result from direct trauma, such as a fall onto the knee.
• Often stable if the fracture is not displaced; may heal well without surgery 2 5 9.

Comminuted Fractures

• Patella breaks into three or more pieces, often due to high-energy trauma like car accidents.
• More likely to involve soft tissue injury and require complex fixation 1 3 6.
• 3D imaging has shown these often have "coronal fragments" and significant lower-patella involvement 3.

Pole (Avulsion) Fractures

• Small fragment avulsed from the top or bottom of the patella, sometimes pulling a tendon with it 1 7.
• In children, this can be a "sleeve fracture," where cartilage and periosteum are pulled off (see below) 7.

Stellate Fractures

• Multiple fracture lines radiate from a central point, creating a star-like pattern.
• Common after a direct blow to the knee 3.

Sleeve Fractures (Children)

• Unique to young patients, where the cartilage and periosteum (the "sleeve") are avulsed, often with little visible bone on X-ray 7.
• Requires a high index of suspicion and sometimes ultrasound for diagnosis.

Causes of Patella Fracture

Patella fractures can happen in a split second, but understanding the underlying causes can help with prevention and risk assessment.

Cause	Mechanism	Typical Scenario	Sources
Direct trauma	Blow or fall onto the knee	Falls, car accidents, sports	1 2 5 6 9
Indirect trauma	Sudden contraction of quadriceps	Jumping, slipping, abrupt movement	1 2 7 8
Low-energy trauma	Minor falls	Elderly, especially women	2 9
High-energy trauma	Severe impact	Motor vehicle accidents, industrial injuries	1 3 5 9
Pediatric mechanisms	Rapid muscle contraction	Running/jumping in children	7

Table 3: Main Causes of Patella Fracture

Exploring the Mechanisms

Direct Trauma

• The most classic cause: a fall directly onto the knee or a blow (e.g., dashboard injury in a car accident) 1 2 5 6 9.
• Often produces comminuted or stellate fracture patterns due to the crushing force 1 3 9.

Indirect Trauma

• Occurs when the quadriceps contracts powerfully while the knee is flexed, such as during:
  • Jumping and landing awkwardly
  • Slipping and trying to prevent a fall 1 2 8
• This mechanism tends to cause transverse fractures, as the patella is pulled apart by muscle force 1 2.

Low-Energy Trauma: The Elderly at Risk

• Most patella fractures in older adults (especially women over 65) result from minor falls—often from standing height 2.
• Osteoporosis and reduced balance contribute to increased risk.

High-Energy Trauma

• Young adults and middle-aged people are more likely to sustain patella fractures from high-energy mechanisms like traffic accidents or industrial injuries 1 3 5 9.

Pediatric Considerations

• In children, sleeve fractures often result from rapid contraction of the quadriceps during running, jumping, or abrupt stopping 7.

Treatment of Patella Fracture

Treating a patella fracture is a nuanced process that depends on the fracture type, patient factors, and the stability of the extensor mechanism. The primary goals are to restore knee function, prevent complications, and return the patient to their previous level of activity.

Treatment Modality	Indication	Key Features/Outcomes	Sources
Non-operative	Non-displaced, stable, intact extensor	Immobilization, early rehab	1 2 6 8 9
Tension band wiring	Displaced transverse or simple 2-part	Gold standard, allows early motion	1 2 5 6 8 11
Plate fixation	Comminuted/multifragmentary	Enhanced stability, fewer complications	1 3 12 13
Cerclage wiring	Elderly, comminuted, percutaneous approach	Minimally invasive, good outcomes	1 4
Partial/total patellectomy	Severe destruction, last resort	Rare, significant function loss	1 6
Pediatric-specific	Sleeve fractures	Prompt reduction, internal fixation	7

Table 4: Treatment Options

Management Strategies

Non-Operative Treatment

• Indicated for non-displaced fractures with an intact extensor mechanism 1 2 6 8 9.
• Includes:
  • Knee immobilization (brace or cast)
  • Early, controlled rehabilitation to prevent stiffness 1 9
• Most patella fractures in Sweden, for example, are managed non-operatively (about 67%) 2.
• Outcomes are generally favorable, but some patients may have persistent pain or weakness 9 10.

Surgical Treatment

When is surgery needed?

• Displacement >2-3 mm, step-off >1-4 mm, or disruption of the extensor mechanism 1 6 8.

Tension Band Wiring (TBW)

• The gold standard for transverse, 2-part fractures 1 2 5 6 8.
• Converts tensile forces into compression at the fracture site—promotes healing 1.
• Early motion is encouraged post-op, but complications can include hardware irritation and loss of fixation if not properly done 11.

Plate Fixation

• Comminuted or multifragmentary fractures benefit from angular stable or fixed-angle plate fixation 1 3 12 13.
• Provides multi-planar stability, especially in osteoporotic bone or complex patterns 3 12 13.
• Studies show fewer complications and better function compared to traditional wiring in complex cases 12 13.

Cerclage Wiring

• Percutaneous cerclage (wire loop around the bone) is a minimally invasive option, especially for elderly patients with comminuted fractures 1 4.
• Provides satisfactory function and low complication rates 4.

Patellectomy (Partial or Total)

• Reserved for severe, non-repairable fractures (e.g., highly comminuted with non-reconstructable bone) 1 6.
• Leads to significant loss of knee strength and function—used only as a last resort 1.

Pediatric Considerations

• Sleeve fractures require urgent reduction and often internal fixation to prevent abnormal patella growth 7.

Rehabilitation and Recovery

Early Motion Matters

• Regardless of treatment, early rehabilitation is crucial to avoid joint stiffness, muscle atrophy, and cartilage degeneration 1 5.
• Physical therapy focuses on gradual range of motion, then strength, balance, and functional activities.

Long-Term Outcomes

• Even after good healing, some patients experience:
  • Knee pain or discomfort with activity
  • Difficulty kneeling or squatting
  • Weakness of the quadriceps (up to 26-31% deficit compared to the uninjured side) 10
• Hardware removal for irritation is common (over 50% in some surgical series) 10 11.

Complications

• Early complications include loss of fixation, infection, and symptomatic hardware 11.
• Modern plating systems may reduce these risks in selected cases 12 13.

Conclusion

Patella fractures, while relatively rare, demand careful attention due to the kneecap's vital role in knee function. Prompt recognition of symptoms, accurate fracture classification, and individualized treatment planning are essential for optimal recovery.

Main Points Covered:

• Patella fractures present with acute pain, swelling, inability to extend the knee, and functional loss.
• Fracture types include transverse, vertical, comminuted, pole/avulsion, stellate, and unique pediatric sleeve fractures.
• Causes range from direct trauma (falls, collisions) to indirect mechanisms (sudden muscle contraction), with low-energy falls common in the elderly and high-energy trauma in younger adults.
• Treatment decisions depend on fracture stability, displacement, patient age, and activity level.
  • Non-operative management is suitable for stable, non-displaced fractures.
  • Surgery (tension band wiring, plate fixation, cerclage) is indicated for displaced or complex fractures.
  • Early rehabilitation is critical for restoring function and minimizing complications.
• Long-term, some patients may experience pain, weakness, or difficulty with activities, emphasizing the importance of tailored rehabilitation and patient counseling.

Understanding these core aspects empowers patients and clinicians to navigate the challenges of patella fractures—optimizing care, maximizing recovery, and returning to an active life.