Patellectomy: Understanding Kneecap Removal, Its Consequences, and Recovery

What happens if patella is removed?

The patella, or kneecap, is a crucial sesamoid bone that significantly enhances the mechanical efficiency of the quadriceps muscle group. Its surgical removal, known as a patellectomy, leads to substantial and often irreversible impairments in knee function, including reduced quadriceps strength, altered gait mechanics, and increased stress on the knee joint.

The Patella: Anatomy and Essential Function

The patella is the largest sesamoid bone in the human body, embedded within the quadriceps tendon where it crosses the knee joint. Its unique position and anatomical structure allow it to serve several critical functions:

• Mechanical Advantage (Fulcrum Effect): The primary role of the patella is to increase the mechanical advantage of the quadriceps femoris muscle. By acting as a fulcrum, it distances the quadriceps tendon from the knee's axis of rotation. This increases the lever arm of the quadriceps, allowing it to generate greater knee extension torque with less muscle force. Without the patella, the quadriceps tendon would sit directly on the femoral condyles, significantly reducing its efficiency.
• Protection: It acts as a shield, protecting the anterior aspect of the knee joint from direct trauma.
• Force Distribution: The patella helps distribute compressive forces across the femoropatellar (patellofemoral) joint during knee flexion and extension, reducing stress on the underlying cartilage.
• Aesthetic and Sensory: Contributes to the normal contour of the knee and provides sensory feedback for proprioception.

Understanding Patellectomy: When and Why it Occurs

Patellectomy is the surgical removal of the patella. It is a procedure rarely performed today due to the severe functional deficits it causes. It is typically considered a last resort in cases of:

• Severe Comminuted Fractures: When the patella is shattered into many pieces, making reconstruction impossible.
• Chronic, Intractable Patellofemoral Pain: In rare instances where all other conservative and surgical treatments for severe patellofemoral pain have failed, and the pain is debilitating.
• Tumors: In the unlikely event of a tumor involving the patella.
• Severe Osteoarthritis of the Patellofemoral Joint: When the joint is completely destroyed and causing severe, unmanageable pain, and other options like arthroplasty are not feasible.

Immediate Post-Operative Consequences

Following a patellectomy, patients experience significant immediate challenges:

• Pain and Swelling: Significant post-surgical pain and swelling are common, requiring robust pain management.
• Immobilization: The knee is often immobilized for a period to allow soft tissue healing and reduce stress on the quadriceps tendon, which now directly articulates with the femur.
• Loss of Extensor Mechanism Integrity: The quadriceps tendon must be reattached to the patellar ligament (now directly to the tibia) or surrounding soft tissues, which significantly alters the knee's extensor mechanism.
• Difficulty with Weight-Bearing: Initial weight-bearing is typically restricted, and walking will require crutches or other assistive devices.

Long-Term Biomechanical and Functional Impacts

The absence of the patella has profound and lasting effects on knee mechanics and function:

• Significant Reduction in Quadriceps Leverage: This is the most critical consequence. Without the patella acting as a fulcrum, the quadriceps muscles lose a substantial portion of their mechanical advantage. This means:
  • Increased Quadriceps Effort: A much greater muscular force is required from the quadriceps to achieve the same amount of knee extension torque.
  • Reduced Strength: Despite increased effort, the overall strength of knee extension is significantly diminished. Daily activities like climbing stairs, rising from a chair, or walking on uneven terrain become very challenging.
• Altered Joint Mechanics and Increased Stress:
  • The quadriceps tendon now directly articulates with the trochlear groove of the femur. This can lead to chondromalacia (cartilage softening/degeneration) or arthritis in the femoral groove due to unaccustomed friction and pressure.
  • The overall load distribution across the knee joint is altered, potentially leading to increased stress on the tibiofemoral (main knee) joint and accelerating the development of osteoarthritis in this compartment.
• Muscle Weakness and Atrophy: Due to the reduced mechanical efficiency and potential disuse or inability to perform full range-of-motion exercises, significant quadriceps atrophy and weakness are common.
• Gait Abnormalities: Patients often develop a characteristic "quadriceps avoidance gait," where they keep the knee relatively straight during the stance phase to minimize the demand on the weakened quadriceps. This can lead to compensatory movements and increased stress on other joints (e.g., hip, ankle, spine).
• Reduced Range of Motion: While some range of motion may be regained, achieving full knee extension or deep flexion can be difficult due to soft tissue scarring, altered mechanics, and pain.
• Chronic Pain and Instability: Many patients experience persistent pain, particularly during activity, and a feeling of instability or giving way in the knee.
• Cosmetic Changes: The knee will appear flattened or concave anteriorly where the patella once was.

Rehabilitation After Patellectomy

Rehabilitation after a patellectomy is long, arduous, and crucial for optimizing what function can be regained. It typically involves:

• Early Range of Motion: Carefully progressing knee flexion and extension to prevent stiffness.
• Progressive Strengthening: Intensive quadriceps strengthening, often starting with isometric exercises and gradually advancing to isotonic and functional movements. Hamstring and gluteal strengthening are also vital to support overall lower limb mechanics.
• Gait Retraining: Learning to walk efficiently and safely with altered knee mechanics.
• Proprioception and Balance Training: To improve stability and neuromuscular control.
• Activity Modification: Patients often need to adjust their daily activities, work, and recreational pursuits to accommodate the permanent changes in knee function.

Quality of Life Considerations

The impact on quality of life after a patellectomy can be substantial. Patients may face limitations in:

• Daily Activities: Difficulty with stairs, squatting, kneeling, and prolonged standing or walking.
• Work: Physically demanding jobs may become impossible.
• Sports and Recreation: Participation in high-impact sports or activities requiring strong knee extension (e.g., running, jumping, cycling) is often severely restricted or impossible.
• Psychological Impact: Chronic pain, functional limitations, and the inability to participate in desired activities can lead to frustration, anxiety, and depression.

Conclusion

The patella, though small, plays an indispensable role in the biomechanics of the knee joint. Its removal, a patellectomy, is a drastic measure with severe and enduring consequences. While it may alleviate intractable pain in specific, dire circumstances, it comes at the high cost of significantly compromised knee function, reduced strength, altered gait, and a substantial impact on a person's ability to perform everyday activities and engage in physical pursuits. Understanding these profound implications underscores why preserving the patella is a paramount goal in knee injury management.