Knee replacement is a kind of arthroplasty that means "surgical repair of a joint" and it involves the surgical replacement and reconstruction of degenerated joints, using prosthetics or artificial body parts.
When the articular cartilage of the knee is worn out or damaged, then instead of sliding over each other, the bones crush and rub each other. This makes the knee hard to move and painful.
The surgeon caps the ends of the bones that form the knee joint with plastic or metal components or implants a prosthetic that is shaped as a joint. With a prosthetic, the patient feels less pain and the knee will move properly.
Knee replacement surgery can help patients whose knee (or knees) has degenerated due to rheumatoid arthritis, osteoarthritis, or post-traumatic arthritis when an injury has damaged the knee.
Type of knee replacement surgery
Knee replacement can be partial or total.
Total Knee Replacement (TKR)
Total knee replacement surgery is the replacement of both sides of the knee joint.
The surgery lasts between 1 to 3 hours. The individual will feel less pain and better mobility but there will be scar tissue, which can make it difficult to bend and move the knees.
Partial knee replacement (PKR)
Partial replacement includes the replacement of only one side of the knee joint. In this procedure, less bone is removed, so a smaller incision is needed but it does not last as long as a total replacement surgery.
Partial knee replacement is suitable for people whose only one part of the knee is damaged.
The recovery period and hospital stay are normally shorter as compare to the total knee replacement surgery.
What is the need for knee replacement surgery?
The three common reasons for knee replacement surgery are:
Osteoarthritis: Osteoarthritis is related to age and caused by the normal wear and tear of the knee joint. It mostly affects the patients of age above 50 years but younger people may have it.
Osteoarthritis is caused by breakdown, inflammation and the eventual and gradual loss of cartilage in the joints. Over time, the cartilage wears down and the bones start rubbing together. To compensate, the bones may grow thicker but this results in more friction that increases the pain.
Rheumatoid arthritis: It is also called inflammatory arthritis; the membrane around the knee joint becomes inflamed and thick. Chronic inflammation damages the cartilage, causing stiffness and soreness.
Post-traumatic arthritis: Post-traumatic arthritis is the result of a severe knee injury. Breaking of the bones around the knee or tearing up the ligaments affects the knee cartilage.
Who might need a knee replacement?
Knee surgery is a suitable option for patients who experience:
- Severe knee pain or stiffness that prevents them from doing everyday tasks and activities such as going upstairs, walking, getting up from a chair and getting in and out of cars.
- Moderate but continuous knee pain that continues even while resting or sleeping
- Chronic knee swelling and inflammation that does not improve after resting or taking medications
- Knee deformity, when there is a noticeable arch on the outside or inside of the knee
- Depression, resulting from the inability to carry out social or daily activities.
Test and diagnosis
- A complete physical examination of the patient as well as several diagnostic tests including blood tests will be done.
- Medical history (such as hemophilia, diabetes, blood pressure and pregnancy), medications and drug allergies if any, should be informed to the doctor before the surgery.
- The patient is advised to avoid smoking for as long as possible before the surgical procedure.
Treatment Procedure for Knee Replacement
Knee Replacement surgery procedure
Knee replacement surgery lasts up to 2-3 hours.
- An intravenous (IV) line is started in your hand or arm & a urinary catheter is inserted.
- The skin over the surgical site will be cleansed with an antiseptic solution.
- The doctor makes an incision in the knee area.
- Then, the surgeon removes the damaged knee joint surface and resurface it with the prosthesis.
- The prosthesis for the knee is made up of metal and plastic. However, a cemented prosthesis is the most common type of artificial knee prosthesis; it attaches to the bone with surgical cement.
- The prosthesis is mostly comprised of 3 components: the tibial component (to resurface the top of the shin or tibia bone), the femoral component (to resurface the end of the thigh bone and the patellar component (to resurface the kneecap bottom that rubs against the thigh bone).
- The incision will be closed with surgical staples or stitches & a drain may be placed in the incision site to remove the fluid.
- A sterile bandage or dressing will be applied.
After the Knee Replacement surgery
- After the surgery, the patient is kept in the recovery room for a few hours.
- The patient will be hospitalised for 4-6 days.
- Most people recover within 12 months after the surgery but the recovery time will differ depending on the age and overall health.
The length and complexity of a total knee replacement operation depend in part on whether both knee joints are replaced during the operation or only one. Such disorders as osteoarthritis usually affect both knees, and some patients would rather not undergo surgery twice. Replacement of both knees is known as bilateral TKR, or bilateral knee arthroplasty. Bilateral knee replacement seems to work best for patients whose knees are equally weak or damaged. Otherwise most surgeons recommend operating on the more painful knee first so that the patient will have one strong leg to help him or her through the recovery period following surgery on the second knee. The disadvantages of bilateral knee replacement include a longer period of time under anesthesia; a longer hospital stay and recovery period at home; and a greater risk of severe blood loss and other complications during surgery.
If the operation is on only one knee, it will take two to four hours. The patient may be given a choice of general, spinal, or epidural anesthesia. An epidural anesthetic, which is injected into the space around the spinal cord to block sensation in the lower body, causes less blood loss and also lowers the risk of blood clots or breathing problems after surgery. After the patient is anesthetized, the surgeon will make an incision in the skin over the knee and cut through the joint capsule. He or she must be careful in working around the tendons and ligaments inside the joint. Knee replacement is a more complicated operation than hip replacement because the hip joint does not depend as much on ligaments for stability. The next step is cutting away the damaged cartilage and bone at the ends of the femur and tibia. The surgeon reshapes the end of the femur to receive the femoral component, or shell, which is usually made of metal and attached with bone cement.
After the femoral part of the prosthesis has been attached, the surgeon inserts a metal component into the upper end of the tibia. This part is sometimes pressed rather than cemented in place. If it is a cementless prosthesis, the metal will be coated or textured so that new bone will grow around the prosthesis and hold it in place. A plastic plate called a spacer is then attached to the metal component in the tibia. The plastic allows the femur and tibia to move smoothly against each other.
Lastly, another plastic component is glued to the rear of the patella, or kneecap. This second piece of plastic prevents friction between the kneecap and the other parts of the prosthesis. After all the parts of the prosthesis have been implanted, the surgeon will check them for proper positioning, make certain that the tendons and ligaments have not been damaged, wash out the incision with sterile saline solution, and close the incision.
PHYSICAL EXAMINATION OF THE KNEE. Following the history, the doctor will examine the knee itself. The knee will be checked for swelling, reddening, bruises, breaks in the skin, lumps, or other unusual features while the patient is standing. The doctor will also make note of the patient's posture, including whether the patient is bowlegged or knock-kneed. The patient may be asked to walk back and forth so that the doctor can check for gait abnormalities.
In the second part of the physical examination , the patient lies on an examining table while the doctor palpates (feels) the structures of the knee and evaluates the strength or tightness of the tendons and ligaments. The patient may be asked to flex one knee and straighten the leg or turn the knee inward and outward so that the doctor can measure the range of motion in the joint. The doctor will also ask the patient to lie still while he or she moves the knee in different directions.
IMAGING STUDIES. The doctor will order one or more imaging studies in order to narrow the diagnosis. A radiograph or x ray is the most common, but is chiefly useful in showing fractures or other damage to bony structures. X-ray studies are usually supplemented by other imaging techniques in diagnosing knee disorders. A computed tomography, or CAT scan, which is a specialized type of x ray that uses computers to generate three-dimensional images of the knee joint, is often helpful in evaluating malformations of the joint. Magnetic resonance imaging (MRI) uses a large magnet, radio waves, and a computer to generate images of the knee joint. The advantage of an MRI is that it reveals injuries to ligaments, tendons, and menisci as well as damage to bony structures.
ASPIRATION. Aspiration is a procedure in which fluid is withdrawn from the knee joint by a needle and sent to a laboratory for analysis. It is done to check for infection in the joint and to draw off fluid that is causing pain. Aspiration is most commonly done when the knee has swelled up suddenly, but may be performed at any time. Blood in the fluid usually indicates a fracture or torn ligament; the presence of bacteria indicates infection; the presence of uric acid crystals indicates gout. Clear, straw-colored fluid suggests osteoarthritis.
ARTHROSCOPY. Arthroscopy can be used to treat knee problems as well as diagnose them. An arthroscope consists of a miniature camera and light source mounted on a flexible fiberoptic tube. It allows the surgeon to look into the knee joint. To perform an arthroscopy, the surgeon will make two to four small incisions known as ports. One port is used to insert the arthroscope; the second port allows insertion of miniaturized surgical instruments ; the other ports drain fluid from the knee. Sterile saline fluid is pumped into the knee to enlarge the joint space and make it easier for the surgeon to view the knee structures and to cut, smooth, or repair damaged tissue.
Aftercare following knee replacement surgery begins while the patient is still in the hospital. Most patients will remain there for five to 10 days after the operation. During this period the patient will be given fluids and antibiotic medications intravenously to prevent infection. Medications for pain will be given every three to four hours, or through a device known as a PCA (patient-controlled anesthesia). The PCA is a small pump that delivers a dose of medication into the IV when the patient pushes a button. To get the lungs back to normal functioning, a respiratory therapist will ask the patient to cough several times a day or breathe into blow bottles.
Aftercare during the hospital stay is also intended to lower the risk of a venous thromboembolism (VTE), or blood clot in the deep veins of the leg. Prevention of VTE involves medications to thin the blood; exercises for the feet and ankles while lying in bed; and wearing thromboembolic deterrent (TED) or deep vein thrombosis (DVT) stockings. TED stockings are made of nylon (usually white) and may be knee-length or thigh-length; they help to reduce the risk of a blood clot forming in the leg vein by putting mild pressure on the veins.
Physical therapy is also begun during the patient's hospital stay, often on the second day after the operation. The physical therapist will introduce the patient to using a cane or crutches and explain how to manage such activities as getting out of bed or showering without dislocating the new prosthesis. In most cases the patient will spend some time each day on a continuous passive motion (CPM) machine, which is a device that repeatedly bends and straightens the leg while the patient is lying in bed. In addition to increasing the patient's level of physical activity each day, the physical therapist will help the patient select special equipment for recovery at home. Commonly recommended devices include tongs or reachers for picking up objects without bending too far; a sock cone and special shoehorn; and bathing equipment.
Following discharge from the hospital , the patient may go to a skilled nursing facility, rehabilitation center, or home. Patients who have had bilateral knee replacement are unlikely to be sent directly home. Ongoing physical therapy is the most important part of recovery for the first four to five months following surgery. The physical therapist will monitor the patient's progress as well as suggest specific exercises to improve strength and range of motion. After the home visits, the patient is encouraged to take up other forms of low-impact physical activity in addition to the exercises; swimming, walking, and pedaling a stationary bicycle are all good ways to speed recovery.