The Knee and Arthritis

The knee joint is stabilized by many key tendons and ligaments, one of which being the medial patellofemoral ligament (MPFL). The MPFL plays a crucial role in stabilizing the patella (kneecap) and preventing it from dislocating laterally. Injury to the MPFL often occurs due to trauma or sports-related activities and impacts, and can lead to recurrent patellar dislocations and instability.

In cases where arthritis or other degenerative changes are confined to just one compartment, a unicompartmental knee arthroplasty (UKA), also known as partial knee replacement, may be a suitable option. This procedure is less invasive than a total knee arthroplasty and involves replacing only the damaged compartment while preserving healthy bone, cartilage, and ligaments in the rest of the knee, giving it a more natural feel after a typically shorter recovery period with less postoperative pain.
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UKA involves a smaller incision compared to the total knee replacement (TKA) procedure, resulting in less disruption to the knee's soft tissues. During the procedure, the surgeon removes the damaged cartilage and shaves off a small portion of the underlying bone from the affected knee compartment. The removed structures are then replaced with a metal and plastic prosthesis. This prosthesis typically includes a metal femoral (upper) component sliding over a plastic tibial (lower) component, and sometimes a plastic patellar component, depending on the specific area being treated. The goal of UKA is to restore smooth joint movement and relieve pain while maintaining as much of the natural knee as possible.

As with all surgeries, a UKA comes with its specific risks, which include:
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● Aseptic loosening: Loosening of the prosthesis over time
● Progression of arthritis in other knee compartments
● Infection of the wound or joint
● Polyethylene wear: Wearing down of the prosthetic material
● Stiffness or limited range of motion
● Injury to nerves or vessels around the knee
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General minor risks associated with surgery and anesthesia include nausea, vomiting, headaches, sore throat, and urinary retention. Major general risks include blood clots, potentially leading to heart attack or stroke, allergic reactions, and pneumonia. Your surgeon will make sure to discuss the relevant risks with you prior to your surgery and take precautions to minimize the risk of any complications.

Before the surgery, your surgeon will have a discussion with you and examine your knee before conducting a thorough presurgical workup, which may include X-rays or MRI of your knee to visualize the extent and location of joint damage, along with blood tests as needed to ensure the surgery is right for you.
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The procedure can be performed under general anesthesia or regional anesthesia (such as spinal or epidural). The choice of anesthesia is based on your medical profile, your care team’s discussion with you, and their assessment.
After your surgery, pain management is a priority. To manage pain effectively after the operation, a multimodal pain control strategy is employed, which consists of combining different modalities to treat your pain, including acetaminophen (e.g. Tylenol), NSAIDs (e.g. Advil, Aleve), opioids (e.g. oxycodone), and potentially nerve blocks, a minor procedure where a regional nerve gets frozen with the injection of a local anesthetic medication.

The recovery period for a UKA is shorter than for a total knee replacement. You can expect to go home the same day of the surgery, provided your surgeon determines that your recovery is on the right track. You should be able to walk right away and will in fact be encouraged to start walking and doing some physiotherapy exercises to ensure you maximize your mobility and strength, although you may need to use crutches to be fully stable for up to two weeks. In the meantime, high-impact activities, such as running or heavy lifting, should be avoided to protect your knee. Full recovery and return to more strenuous activities such as sports generally take about three months.
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Your pain will most likely be managed using a multimodal pain control strategy as described above, and your surgeon may also prescribe additional medication to reduce your risk of blood clots. Regular follow-up visits with your surgeon will help monitor your recovery and ensure your new prosthesis is functioning correctly.