Patellectomy: Understanding Kneecap Removal, Its Effects, and Rehabilitation

What happens if your kneecap is removed?

The removal of the kneecap, known as a patellectomy, leads to significant alterations in knee biomechanics, primarily reducing the quadriceps muscle's mechanical advantage, decreasing overall leg strength, and compromising the knee joint's protection.

Understanding the Patella's Role

The kneecap, or patella, is a unique bone classified as a sesamoid bone, meaning it's embedded within a tendon—specifically, the quadriceps tendon. It sits anterior to the knee joint, articulating with the trochlear groove of the femur (thigh bone). Its seemingly small size belies its critical functions:

• Mechanical Advantage (Lever Arm): The patella acts as a fulcrum, increasing the lever arm of the quadriceps muscle. By pushing the quadriceps tendon further away from the knee's center of rotation, it significantly enhances the quadriceps' ability to extend the knee, making movements like standing up, climbing stairs, and jumping far more efficient and powerful.
• Force Transmission: It helps distribute compressive forces across the femoropatellar joint during knee flexion and extension, reducing stress on the quadriceps tendon and the underlying femur.
• Protection: The patella provides a bony shield for the anterior aspect of the knee joint, protecting the femoral condyles and underlying soft tissues from direct impact.

What is a Patellectomy?

A patellectomy is the surgical removal of the patella. This procedure is typically a last resort, reserved for severe cases where the patella is irreparable or causes intractable pain and dysfunction. Common reasons for a patellectomy include:

• Severe Comminuted Fractures: When the patella shatters into many pieces, making reconstruction impossible.
• Severe Patellofemoral Arthritis: In cases of end-stage arthritis where conservative treatments and other surgical options have failed, and pain is debilitating.
• Tumors: Rarely, the presence of a tumor within the patella may necessitate its removal.
• Chronic Patellar Instability or Pain: In very rare, extreme cases where other treatments for chronic dislocation or pain are unsuccessful.

Immediate Post-Operative Effects

Following a patellectomy, the immediate phase focuses on managing pain, swelling, and initiating early, controlled motion to prevent stiffness and scar tissue formation.

• Pain and Swelling: Significant discomfort and swelling are common, managed with medication and RICE (Rest, Ice, Compression, Elevation) principles.
• Immobility/Bracing: The knee is often immobilized in an extension brace initially to protect the healing soft tissues and allow for early quadriceps re-education without excessive stress.
• Rehabilitation Initiation: Physical therapy begins almost immediately, focusing on gentle range of motion exercises, isometric quadriceps contractions, and pain management.

Long-Term Consequences of Patella Removal

The absence of the patella profoundly impacts knee function and biomechanics, leading to several predictable long-term consequences:

• Significant Loss of Quadriceps Strength: This is the most notable and immediate functional deficit. Without the patella acting as a lever, the quadriceps tendon now lies closer to the knee's axis of rotation. This effectively shortens the lever arm, meaning the quadriceps must work much harder to generate the same amount of knee extension force. Patients typically experience a 30-50% reduction in quadriceps strength, making activities requiring strong knee extension (e.g., climbing stairs, rising from a chair, squatting, jumping) considerably more difficult.
• Increased Stress on the Quadriceps Tendon: The quadriceps tendon, previously gliding over the smooth articular surface of the patella, now directly rubs against the femoral condyles. This can lead to:
  • Friction and Irritation: Chronic irritation and inflammation of the quadriceps tendon, potentially leading to tendinopathy.
  • Increased Risk of Rupture: The tendon is subjected to higher direct stresses, increasing its vulnerability to rupture, particularly during forceful contractions.
• Reduced Protection for the Knee Joint: The femoral condyles, once shielded by the patella, are now exposed. This makes the knee joint more susceptible to direct trauma, which can damage the articular cartilage of the femur and tibia.
• Altered Knee Biomechanics and Gait: The entire kinetic chain of the lower limb is affected.
  • Abnormal Joint Mechanics: The altered path of the quadriceps tendon can lead to abnormal tracking and loading patterns within the tibiofemoral joint, potentially accelerating wear and tear.
  • Gait Deviations: Patients may develop compensatory gait patterns, such as a "quadriceps avoidance gait," to minimize stress on the weakened quadriceps and avoid full knee extension under load.
• Chronic Pain and Stiffness: Despite the removal of the source of initial pain, many patients experience persistent pain, often due to scar tissue formation, altered biomechanics, or secondary issues like tendinopathy. Stiffness, particularly in deep knee flexion, is also common due to surgical scarring and altered soft tissue mechanics.
• Functional Limitations: High-impact activities, sports requiring explosive leg power, and even prolonged walking or standing can be challenging. Patients may need to significantly modify their physical activity levels and lifestyle.

Rehabilitation and Adaptation

Living without a patella necessitates a rigorous and lifelong commitment to physical rehabilitation. The primary goals of post-patellectomy rehabilitation are:

• Restore Range of Motion: Gradually regain full knee flexion and extension, addressing scar tissue limitations.
• Maximize Quadriceps Strength: Despite the mechanical disadvantage, strengthening the remaining quadriceps muscle is paramount. This involves progressive resistance exercises, often focusing on closed-chain movements (e.g., leg presses, squats to tolerance) to safely build strength.
• Compensatory Muscle Strengthening: Strengthening other muscles that contribute to knee stability and lower limb function, such as the hamstrings, glutes, and core, is crucial to compensate for the quadriceps deficit.
• Gait Training and Balance: Re-educating proper walking patterns and improving balance to reduce fall risk and improve functional mobility.
• Activity Modification: Learning how to perform daily activities with less strain on the knee and modifying exercise routines to accommodate the altered biomechanics.

Living Without a Patella

While a patellectomy represents a significant functional compromise, many individuals can achieve a reasonable quality of life with dedicated rehabilitation and appropriate activity modifications. The degree of functional recovery varies widely depending on the individual's pre-operative condition, surgical technique, and commitment to physical therapy. While high-level athletic performance is generally not achievable, many can return to daily activities and light recreational pursuits. Long-term follow-up and management of potential secondary issues like tendinopathy or early-onset osteoarthritis are often necessary.

Conclusion

The patella, though small, plays a disproportionately large role in knee function, acting as a crucial biomechanical amplifier for the quadriceps muscle and a protective shield for the joint. Its removal, a patellectomy, is a procedure of last resort that fundamentally alters knee mechanics, leading to a permanent reduction in quadriceps strength, increased stress on the quadriceps tendon, and reduced joint protection. While diligent rehabilitation can help mitigate these effects and improve functional outcomes, individuals living without a kneecap must adapt to lifelong changes in their physical capabilities and activity levels.