Lateral Full Knee Replacement: Clarifying the Term, Total Knee Arthroplasty, and Partial Knee Replacement

What is lateral full knee replacement?

The term "lateral full knee replacement" is not a standard medical designation; a "full" knee replacement typically refers to a Total Knee Arthroplasty (TKA) which addresses all three compartments of the knee. Procedures specifically targeting only the lateral compartment are known as Lateral Unicompartmental Knee Arthroplasty (UKA) or partial knee replacements, while the lateral compartment is one of the areas replaced during a total knee replacement.

Understanding Knee Anatomy and Replacement Terminology

To fully grasp the concept of knee replacement, it's essential to understand the knee's intricate anatomy. The knee is a complex hinge joint formed by the articulation of three bones: the femur (thigh bone), tibia (shin bone), and patella (kneecap). Within this joint, there are three distinct compartments:

• Medial Compartment: The inner side of the knee, between the medial femoral condyle and the medial tibial plateau.
• Lateral Compartment: The outer side of the knee, between the lateral femoral condyle and the lateral tibial plateau.
• Patellofemoral Compartment: The front of the knee, between the patella and the trochlear groove of the femur.

Degenerative conditions like osteoarthritis can affect one, two, or all three of these compartments. The type of knee replacement surgery performed depends on which compartments are damaged.

Clarifying "Lateral Full Knee Replacement"

The phrase "lateral full knee replacement" can be misleading because:

• "Full" typically refers to a Total Knee Arthroplasty (TKA): A TKA involves replacing the articular surfaces of the medial, lateral, and patellofemoral compartments. It's a comprehensive procedure addressing widespread damage throughout the joint.
• "Lateral" refers to a specific compartment: If only the lateral compartment is diseased, the appropriate procedure is a Lateral Unicompartmental Knee Arthroplasty (UKA), also known as a partial knee replacement. This procedure specifically targets and replaces only the damaged cartilage and bone in the lateral compartment, preserving the healthy cartilage and ligaments in the medial and patellofemoral compartments.

Therefore, "lateral full knee replacement" is likely either a misinterpretation of a Total Knee Arthroplasty where the lateral compartment is one of the areas being replaced, or a conflation of a Lateral Unicompartmental Knee Arthroplasty with the term "full" which is usually reserved for total replacements.

Total Knee Arthroplasty (TKA): The "Full" Replacement

A Total Knee Arthroplasty (TKA) is a major surgical procedure performed to relieve pain and disability caused by severe arthritis or trauma to the knee joint. It is considered when all three compartments of the knee are significantly damaged.

Key aspects of TKA:

• Comprehensive Replacement: Both the medial and lateral compartments of the tibiofemoral joint, as well as the patellofemoral joint, are resurfaced with prosthetic components.
• Indications: Typically reserved for individuals with widespread, severe osteoarthritis, rheumatoid arthritis, or post-traumatic arthritis affecting multiple compartments, where conservative treatments have failed.
• Outcome: Highly effective in reducing pain and improving function for most patients.

Lateral Unicompartmental Knee Arthroplasty (UKA): A Partial Approach

If only the lateral compartment of the knee is significantly damaged, and the other compartments (medial and patellofemoral) are healthy, a Lateral Unicompartmental Knee Arthroplasty (UKA) may be an option.

Key aspects of Lateral UKA:

• Targeted Replacement: Only the damaged bone and cartilage in the lateral compartment are removed and replaced with prosthetic components. The healthy parts of the knee, including the anterior and posterior cruciate ligaments, are preserved.
• Indications: Suitable for patients with isolated, severe arthritis in the lateral compartment, intact ligaments, and good alignment of the unaffected compartments.
• Advantages (compared to TKA):
  • Smaller incision and less soft tissue dissection.
  • Potentially faster recovery and rehabilitation.
  • More natural knee motion and proprioception due to preserved ligaments.
  • Lower risk of certain complications associated with TKA.
• Disadvantages:
  • Not suitable if arthritis is present in other compartments or if ligamentous instability exists.
  • May require conversion to a TKA later if arthritis develops in the preserved compartments.

When is Knee Replacement Surgery Indicated?

Regardless of whether it's a TKA or a UKA, knee replacement surgery is generally considered when:

• Severe Pain: Chronic knee pain that significantly interferes with daily activities, sleep, and quality of life.
• Functional Limitations: Difficulty walking, climbing stairs, getting in and out of chairs, or participating in desired physical activities.
• Failure of Conservative Treatments: Non-surgical options such as physical therapy, medications (NSAIDs), injections (corticosteroids, hyaluronic acid), bracing, and activity modification have not provided adequate relief.
• Radiographic Evidence: X-rays show significant joint damage, cartilage loss, and bone-on-bone articulation.

The Surgical Procedure: A Brief Overview

Both TKA and UKA are performed under regional or general anesthesia.

1. Incision: An incision is made over the front of the knee.
2. Exposure: The knee joint is exposed, and the patella is typically moved aside.
3. Bone Preparation: The damaged cartilage and a small amount of underlying bone are precisely removed from the femur, tibia, and (for TKA) the patella.
4. Implant Insertion: Metal components are cemented or press-fit onto the prepared bone surfaces. A plastic (polyethylene) spacer is inserted between the metal components to create a smooth gliding surface. For TKA, a plastic button may also be placed on the back of the patella.
5. Joint Assessment: The surgeon checks the stability, alignment, and range of motion of the new joint.
6. Closure: The incision is closed in layers.

Recovery and Rehabilitation

Recovery from knee replacement surgery is a critical phase, heavily reliant on a structured rehabilitation program.

• Immediate Post-Op: Pain management is a priority. Patients typically begin gentle movement and weight-bearing (often with assistance) within hours or the first day after surgery.
• Physical Therapy: A cornerstone of recovery. A physical therapist will guide patients through exercises designed to:
  • Restore range of motion.
  • Strengthen the quadriceps, hamstrings, and surrounding musculature.
  • Improve balance and gait.
• Timeline:
  • Hospital Stay: Typically 1-3 days.
  • Home Recovery: Walking with aids (walker, crutches, cane) for several weeks.
  • Return to Activities: Most daily activities can be resumed within 6-12 weeks. Full recovery and return to more strenuous activities can take 6 months to a year.
• Patient Compliance: Adherence to the physical therapy regimen is paramount for achieving optimal outcomes.

Potential Risks and Complications

While generally safe and effective, knee replacement surgery carries potential risks, including:

• Infection: Around the surgical site or within the joint.
• Blood Clots: In the leg veins (DVT) or lungs (PE).
• Nerve or Blood Vessel Damage: Rare, but possible during surgery.
• Stiffness or Limited Range of Motion: Despite therapy.
• Implant Loosening or Wear: Can occur over time, potentially requiring revision surgery.
• Fracture: Of the bone around the implant.
• Persistent Pain: Though rare, some patients may continue to experience pain.

Living with a Knee Replacement

With proper care and rehabilitation, most individuals experience significant pain relief and improved function after knee replacement surgery.

• Activity Modification: While many activities are possible, high-impact sports (e.g., running, jumping, contact sports) are generally discouraged to protect the longevity of the implant. Low-impact activities like swimming, cycling, and walking are highly recommended.
• Regular Follow-ups: Periodic check-ups with the orthopedic surgeon are necessary to monitor the implant and overall knee health.
• Implant Longevity: Modern knee replacements are designed to last 15-20 years or more, but individual results vary based on activity level, weight, and overall health.

Conclusion

The term "lateral full knee replacement" is a blend of concepts that, when clarified, point to either a Total Knee Arthroplasty (TKA), which replaces all knee compartments including the lateral, or a Lateral Unicompartmental Knee Arthroplasty (UKA), a partial replacement specifically for the lateral compartment. Both procedures aim to alleviate pain and restore function in a severely damaged knee. Understanding the distinct indications, surgical approaches, and rehabilitation requirements for each is crucial for patients, fitness professionals, and anyone interested in advanced orthopedic interventions. Consulting with an orthopedic surgeon is essential for an accurate diagnosis and to determine the most appropriate treatment strategy for individual knee conditions.