Introduction
The knee is a crucial joint that bears the weight of your body, facilitating movement and walking. Comprised of bones, ligaments, and cartilage, it features two types of cartilage: one that covers the bones and another that cushions them.
Knee injuries are the most prevalent type of joint injury, often involving not only bones but also ligaments, tendons, and cartilage. Factors such as sports activities and accidents commonly lead to these injuries. Conditions like arthritis can also affect the knee.
Common symptoms of knee injuries include pain, difficulty bearing weight, stiffness, instability, swelling, and bruising from acute injuries.
If an injury or arthritis impacts only a specific area of the knee, your physician may discuss the option of a partial knee replacement. This recommendation typically arises after non-surgical treatments—such as injections, medications, and physical therapy—have proven ineffective. Partial knee replacement is ideal for individuals with arthritis localized to one compartment of the knee or other joint issues confined to a specific area.
During surgery, the damaged bone and tissue are removed and replaced with metal and plastic components, while the remaining healthy bone and tissue are preserved. Many patients report a successful recovery, experiencing shorter healing times, less blood loss during surgery, and reduced pain compared to those undergoing total knee replacement.
Anatomy
The knee operates as a hinge joint, connecting the thighbone (femur) to the shinbone (tibia). It also includes the smaller fibula alongside the tibia and the kneecap (patella) at the front. The knee is stabilized by ligaments—strap-like tissues that connect bones—and tendons that link muscles to bones.
- Anterior Cruciate Ligament (ACL): Prevents the tibia from sliding forward relative to the femur.
- Posterior Cruciate Ligament (PCL): Stops the tibia from sliding backward on the femur.
- Collateral Ligaments: These ligaments on either side of the knee prevent lateral movement.
Menisci: Two cartilage cushions (medial and lateral) absorb shock and prevent friction between the femur and tibia. Additionally, small sacs called bursae within the joint provide lubrication for smooth movement.
Causes
- Osteoarthritis
Osteoarthritis is the most prevalent form of arthritis, affecting approximately 21 million Americans. It typically develops with age and can result from excessive joint use due to sports or labor.
Arthritis is the leading reason for requiring a partial knee replacement. It causes inflammation and damage to the knee's cartilage, leading to wear and tear. As the cartilage diminishes, the bones may grind against each other, resulting in painful bone spurs that exacerbate discomfort and hinder movement. This degeneration usually occurs gradually, often over years, before surgery becomes necessary.
- Other Issues
In some cases, individuals may require partial knee replacement following a previous injury, such as a car accident or other trauma affecting the cartilage or ligaments. However, patients with rheumatoid arthritis are typically not suitable candidates for partial knee replacement, as this condition affects the entire joint rather than a specific area.
Symptoms
Arthritis-related knee issues are most common in individuals over 50, but younger patients can also experience these problems, albeit rarely. Regardless of age, it’s crucial to seek medical attention for knee pain. Obesity may contribute to arthritis symptoms, and genetics can play a role; a family history of knee replacements can increase your likelihood of needing the procedure.
Common arthritis symptoms include:
- Pain
- Swelling
- Stiffness
- A sensation of the knee giving way
- Tenderness around the knee
- Fluctuating symptoms with weather changes
- Good and bad days regarding knee pain
Diagnosis
To diagnose the underlying cause of your knee issues, your doctor will review your medical history and any past knee injuries. It’s helpful to note any relevant details and bring someone along for support if necessary. A physical examination and observation of your gait will follow.
An X-ray will be required to assess the space between your femur and tibia. A reduction in this space indicates cartilage deterioration. Blood tests may be performed to rule out rheumatoid arthritis, and joint fluid may be analyzed if swelling is present.
Treatment
- Non-Surgical Approaches
If you’re considering a partial knee replacement, you likely have already attempted non-surgical options. If not, your doctor will encourage you to start with these methods, which may include weight loss, changes in your exercise regimen, supportive braces, medication, or physical therapy. Injections into the knee can also provide relief for weeks or months, potentially delaying the need for surgery.
- Surgical Options
Surgical intervention involves replacing the damaged cartilage with metal or plastic components. The surgeon replaces the arthritic area with a metal cap and inserts a plastic liner, allowing smooth movement and alleviating pain caused by damaged tissue.
Your doctor will carefully analyze your X-rays to determine the most affected areas and ascertain if you qualify for a partial replacement. If advanced arthritis is present, a total knee replacement may be necessary. Your physician will assist you in making the best choice for your situation.
Surgery
On the day of surgery, your doctor will provide specific instructions, and you may be admitted to a hospital. Many procedures are now performed on an outpatient basis, allowing you to return home the same day. Your doctor will determine whether an overnight stay is necessary.
Before the surgery, the anesthesiologist will evaluate your medical history. Some patients receive spinal anesthesia to remain awake but numb, while others prefer general anesthesia. Your doctor will discuss these options with you.
To prevent mistakes, your doctor will sign your knee to confirm which one is being operated on.
A typical partial knee replacement lasts 1-2 hours. The surgeon will make an incision at the front of your knee and verify the arthritis is localized. If it affects more than one area, a total knee replacement may be performed instead. You’ll have consented to this possibility prior to the procedure.
If eligible for a partial replacement, the surgeon will carefully remove the damaged bone and cartilage, capping the bones with smooth metal components cemented in place. A new plastic liner will then be positioned between the metal caps.
Post-surgery, you’ll spend about an hour in recovery before being transferred to a hospital room or discharged to go home.
Recovery
Due to the minimally invasive nature of partial knee replacements, recovery tends to be faster compared to total knee replacements. Most patients can put weight on their knee immediately after surgery, although you may require a walker, cane, or crutches for support.
Your doctor may suggest beginning physical therapy or provide home exercises to enhance knee movement and flexibility. It’s essential to refrain from vigorous activities until your doctor approves. Regular follow-up appointments will help monitor your progress and inform you when normal activities can resume.
While recovery timelines can vary, most patients can drive or return to work within a few weeks. High-impact activities (like running) should be avoided, and adjustments to your routines may be necessary to ensure your knee replacement lasts for years.
Complications
Every surgical procedure carries risks. Your doctor will discuss potential complications with you prior to the surgery. Possible issues following a partial knee replacement include:
- Blood Clots: Deep vein thrombosis can occur, and blood thinners may be administered to mitigate this risk.
- Infection: There’s always a risk of infection with surgery. Typically, antibiotics are given before the procedure.
- Persistent Pain or Nerve Damage: While uncommon, nerve damage may occur during surgery, and there’s a possibility that some pain may persist post-operatively.
