Knee replacement: How does it work?

Knee arthroplasty also known as knee replacement resurfaces a knee with the help of a surgical procedure that has been damaged by arthritis. Various types of arthritis can affect the knee joint. Osteoarthritis is one of the common occurrences. It is a degenerative joint disease that mostly affects middle-aged and older adults. It causes the breakdown of the joint cartilage and the adjacent bones in the knees. Pain and stiffness can also arise from rheumatoid arthritis which causes inflammation of the synovial membrane and results in excessive synovial fluid. It can also result from traumatic arthritis which is a type of arthritis that arises from injury and causes damage to the cartilage.

Some of the medical treatments for degenerative joint diseases are anti-inflammatory medication, glucosamine and chondroitin sulfate, pain medications, limiting painful activities, assistive devices for walking, physical therapy, cortisone injections, and weight loss. Sometimes medical treatments are not satisfactory. In such cases, knee replacements prove to be a better option.

In a knee replacement surgery, the damaged knee joint is replaced with a man-made artificial joint called a prosthesis. Damaged bone and cartilage are removed from the knee joint and then the artificial pieces are placed in the knee. These pieces can be placed in the lower end of the thigh bone. This bone is called the femur and the replacement part is usually made of metal. The pieces can also be put in the upper end of the shin bone. This bone is called the tibia. The replacement parts are usually made of metal and strong plastic. The final part where the pieces can be fitted is the backside of the kneecap. It is called the patella. Here the replacement part is usually made from strong plastic.

During the surgery, there are two types of anesthesia that are used, general anesthesia which puts the patient into asleep and the individual cannot feel pain, or regional (spinal or epidural) anesthesia which makes the patient go numb below the waist. It is usually combined with medicine for sleep. After the anesthesia takes effect, the surgeon makes a cut above the knee which is about 8 to 10 inches. The first step involves removing the kneecap. Then he cuts the thigh bone and the shin bone to fit the replacement part. The underside of the kneecap is then cut to prepare it for new pieces that will be attached there. The two parts of the prosthesis are then attached to the bone. One part is attached to the thigh bone and the other part is attached to the shin bone. Bone cement or screws are used to attach the prosthesis to the bones. Special bone cement is then used to attach the underside of the kneecap. The muscles and tendons surrounding the knee joint are them repaired and the surgical cut is closed. A knee replacement surgery takes about 2 hours.

Once the patient is home, there are certain precautions that should be taken. Following the bathing instructions of the doctor, keeping the leg elevated, applying ice when necessary, taking pain relievers as recommended by the doctor, notifying the doctor immediately if the patient is experiencing fever, redness, swelling, bleeding or other drainages from the incision or increased pain around the incision site are some of them. One should also avoid driving and falling. Sometimes it is advised to use assistive devices while walking.

The results of total knee replacement surgery are often excellent. The operation relieves pain for most people. Most artificial knee joints last from 10 to 15 years. Some last as long as 20 years before it loosens and needs to be replaced. Therefore it is important to have the surgery at the correct time because often the results of the second surgery for replacing the old prosthesis are not satisfactory.

Reference

  1. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/knee-replacement-surgery-procedure
  2. https://medlineplus.gov/ency/article/002974.htm

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