Partial knee replacement, also known as unicompartmental knee arthroplasty, is a surgical procedure in which only the damaged compartment of the knee joint is replaced with an artificial implant. This procedure is an alternative to total knee replacement for patients who have arthritis or damage confined to a specific area of the knee, typically the inner (medial) or outer (lateral) compartment.

Indications for Partial Knee Replacement

• Localized Osteoarthritis: The most common reason for partial knee replacement is osteoarthritis confined to one compartment of the knee.
• Good Overall Knee Health: The procedure is generally recommended for patients whose ligaments (like the anterior cruciate ligament, ACL) are intact and who have no significant damage to the other compartments of the knee.
• No Inflammatory Arthritis: Patients with inflammatory arthritis (like rheumatoid arthritis) are usually not candidates for partial knee replacement.
• Stable Knee Joint: The knee must be stable with good range of motion.

The Surgical Procedure

1. Preoperative Evaluation

   • Medical Assessment: Comprehensive assessment, including imaging (X-rays, MRI), to confirm that the damage is localized to one compartment.
   • Planning: Determining the type of implant and the specific approach based on the patient’s anatomy and condition.

2. Surgery

   • Anesthesia: The surgery is performed under general or spinal anesthesia.
   • Incision: A smaller incision is made compared to total knee replacement, typically on the front or side of the knee.
   • Removal of Damaged Tissue: Only the damaged cartilage and bone from the affected compartment are removed.
   • Implant Placement: A prosthetic component is placed in the affected compartment. The other healthy compartments are left intact.
   • Alignment and Balance: The surgeon ensures that the implant is properly aligned and balanced to function harmoniously with the rest of the knee joint.
   • Closure: The incision is closed with sutures or staples, and a dressing is applied.

Advantages of Partial Knee Replacement

• Less Invasive: The procedure involves a smaller incision and less disruption of the knee tissue, leading to a quicker recovery.
• Faster Recovery: Patients often experience a shorter hospital stay, quicker rehabilitation, and faster return to daily activities.
• Preservation of Healthy Tissue: Since only the damaged part of the knee is replaced, the healthy cartilage, ligaments, and bone are preserved, maintaining more natural knee movement.
• Reduced Pain: Patients typically experience less postoperative pain compared to total knee replacement.
• Lower Risk of Complications: There is a lower risk of complications such as infection and blood clots.

Postoperative Care and Recovery

1. Hospital Stay

   • Most patients are able to go home the same day or the day after surgery.
   • Pain is managed with medications, and early mobilization is encouraged.

2. Physical Therapy

   • A physical therapy program is initiated soon after surgery to restore strength, flexibility, and range of motion in the knee.
   • Most patients can return to normal activities within 3-6 weeks.

3. Rehabilitation

   • Rehabilitation focuses on exercises to strengthen the muscles around the knee and improve joint mobility.

4. Long-Term Care

   • Regular follow-up appointments are necessary to monitor the knee’s function and the integrity of the implant.
   • Patients are advised to avoid high-impact activities to prolong the life of the implant.

Risks and Complications

• Progression of Arthritis: Over time, arthritis may develop in the other compartments of the knee, possibly requiring additional surgery or conversion to total knee replacement.
• Implant Loosening: The implant may loosen or wear out over time, leading to pain and reduced function.
• Infection: Though rare, infection is a potential risk with any surgical procedure.
• Stiffness or Limited Range of Motion: Some patients may experience stiffness or limited mobility after surgery.

Outcomes

• Pain Relief: Most patients experience significant pain relief and improved knee function.
• Preserved Knee Function: By retaining the healthy parts of the knee, patients often report more natural knee movement compared to total knee replacement.
• Durability: Partial knee replacements can last many years, though they may not be as durable as total knee replacements, especially in younger, more active patients.