Knee Replacement

Knee replacement surgery (also called knee arthroplasty) replaces all or part of worn-out or injured knee joints. The damaged bone and cartilage of the knee are removed, and parts made of metal and plastic, called a prosthesis, are implanted in their place.

The goal of the surgery is to relieve pain, improve mobility, restore function, and help people to return to daily activities and improve their quality of life.

Symptoms that indicate a knee replacement may be needed include the following:

• Joint pain
• Stiffness
• Limited mobility or trouble moving the knee
• Swelling

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What is “limited mobility”? For symptoms to be considered severe enough to warrant knee replacement, people are frequently unable to walk more than a block and to go up and down stairs, says Susan Goodman, MD, a rheumatologist and researcher at the Hospital for Special Surgery in New York City. Dr. Goodman specializes in working with people throughout the process of knee and hip replacements.

“They may be awakened at night with pain and walk with a limp. These symptoms are unlikely to respond to simple interventions like ibuprofen or Tylenol. Since knee pain may be referred from other sites such as the hip or the knee, it is important that the X-ray reveals advanced damage to confirm that the knee is the source of the pain,” she says.

Typically, the physician would also use an MRI (magnetic resonance imaging) to look for evidence of advanced knee damage with loss of cartilage.

“The physical exam by the physician will validate the findings from the history and X-rays, with discomfort elicited with knee motion as well as loss of motion, as the severely damaged knee may not extend fully or flex fully,” says Goodman.

The knee joint is composed of three bones: the femur (thighbone), the patella (kneecap), and the tibia (shinbone).

Once the damaged bone and cartilage are removed, the artificial parts are attached.

Total Knee Replacement

Partial Knee Replacement

For a partial knee replacement (PKR) procedure, only the damaged part of the knee is replaced. Generally, this may be an option for people who have arthritis in only one portion of the knee and who have intact knee ligaments. This surgery is also called partial knee resurfacing surgery or unicompartmental knee replacement, or “uni.”

Surgical Expertise and Robotic Assistance

The type of knee surgery that your surgeon is most comfortable and experienced with should also influence the decision, says Goodman.

Before undergoing knee replacement surgery, your surgeon will provide specific instructions to help ensure a successful procedure. Preparation recommendations may vary according to a person’s health history and individual risks.

Steps may include the following:

Preoperative Testing These may include a physical exam, blood tests, X-rays, and possibly an electrocardiogram (ECG or EKG) to assess your overall health.

Stop Certain Medications Blood thinners and other medications that might increase the risk of bleeding will need to be temporarily discontinued for surgery.

Fasting You may be asked to refrain from eating or drinking for 8 to 12 hours before surgery to prevent complications related to anesthesia.

Physical Preparation You might be advised to start physical therapy beforehand to strengthen the muscles around the knee and improve flexibility.

A knee replacement procedure is typically performed in a hospital or specialized surgery center under general or regional anesthesia, ensuring that you are either asleep or numbed from the waist down.

The surgery usually takes one to two hours. An incision is made over the knee, and the surgeon removes all the damaged bone and cartilage. The replacement parts are then attached to the healthy bone that remains.

Your care team will get you up and walking within a few hours. After you leave the hospital, you’ll have physical therapy for several weeks. Most people are able to walk without a walker or cane about six weeks after knee replacement surgery.

When a person needs both knees replaced, the decision to proceed with both under the same anesthesia is based on the overall health status of the person, says Goodman.

“The likelihood of complications as well as a more difficult recuperation are significantly higher when both are done together. This approach places more stress on the heart and lungs as well as a higher risk of blood clots and should be discussed with the patient’s internist or cardiologist before undertaking it,” she says.

Even in someone with no medical problems, the recuperation is much more stressful and difficult. In general, it is better to separate the replacements by at least three months, says Goodman.

Although thousands of knee replacements are safely performed each year, there is a risk of potential adverse events during the surgery.

Problems With Anesthesia

There are three categories of anesthesia:

• Local This numbs the specific area being treated. Local anesthesia may be used in addition to the main type of anesthesia used in knee replacement surgery.
• Regional This involves blocking nerves to a specific area of the body. With regional anesthesia, you remain conscious, though sedatives are used to help put you in a light sleep.
• General This affects the entire body and causes temporary unconsciousness.

There are risks to anesthesia. In regional anesthesia, there can be side effects such as headache, trouble urinating, allergic reactions, or (rarely) nerve injury.

Bleeding

It’s normal to lose blood during and after knee replacement surgery, and some people need a blood transfusion during surgery or during their recovery.

In the hours, days, and weeks after surgery, your healthcare team — and you — will need to monitor your knee and take steps to support its healing. You may need some help at home during your initial recovery period. Care generally includes:

Postoperative Monitoring While still in the hospital, you will be monitored by staff for signs of infection, blood clots, and proper healing.

Pain Management Your doctor will prescribe pain medications to help you manage discomfort. Nonsteroidal anti-inflammatory drugs (NSAIDs), acetaminophen (Tylenol), or opioids may be used, depending on your needs.

A combination of medications may be used for pain relief as well as to minimize the need for opioids. In some cases, a series of regional blocks using local anesthetics may be used.

• Ice and elevate your knee. Icing your knee a few times a day for 20 minutes at a time will help relieve pain and swelling. Keep your knee above the level of your heart as often as possible by propping it up on cushions or pillows while lying down, or rest it on a footstool if you’re sitting in a chair.
• Keep your incision clean and covered. Follow your surgeon’s instructions. Ask when you should change the dressing on your incision site and when it’s safe to take a shower or bathe.
• Do prescribed exercises. Your surgeon will give you exercises to do soon after your surgery. Follow their instructions on when to begin and how often to perform the movements.

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Follow-Up Appointments You will need to see your medical provider in the days or weeks following surgery to ensure proper healing and assess the function of the new knee joint.

Physical Therapy Most people can start exercising their “new” knee hours after surgery. You may be advised to limit weight-bearing on the knee and avoid certain movements for a few weeks.

As with any major surgery, there is a risk of complications, which may include the following:

Infection Infections can occur in the surgical site or deeper in the joint around the prosthesis. It may happen within days or weeks of the surgery, but it can also occur years later. Minor infections can be treated with antibiotics, but in some people, more surgery or removal of the prosthesis may be necessary.

Blood Clots Blood clots in the legs (deep vein thrombosis) can develop after surgery, posing a risk if they travel to the lungs (pulmonary embolism). Your doctor may prescribe measures to reduce the risk, including periodic evaluation, support stockings, or blood thinners.

Most people do quite well with knee replacement surgery, says Goodman.

“It is a very successful operation. There is typically a marked improvement in pain and restoration of function beginning weeks after surgery with continued improvement over several months,” she says.

The success of total knee replacement in people under 60 is 90 to 95 percent, and an implant can last from 15 to 25 years. For people who have the surgery earlier in life, a revision may be required, but often that’s just an exchange of the plastic insert, meaning that means most of the original implant can stay put.

There are things you can do before and after the replacement surgery to achieve the best outcomes, says Goodman, including the following:

• Discuss your overall medical state with your internist prior to considering knee replacement so that medical problems like diabetes, bleeding risk, infection risk, hypertension, or heart disease can be optimally controlled. “Undergoing surgery with poorly controlled diabetes can increase complications including infection,” Goodman says.
• Because having obesity can also increase the risk of surgical complications, including blood clots or infection, weight reduction should be considered. “However, it is not clear how best to accomplish this. Bariatric surgery for weight reduction may not decrease complications related to obesity after knee replacement, and not much is known about use of weight loss medications for weight reduction prior to surgery,” she says.
• Smoking is another clear risk factor for poor outcomes. “If cessation is not feasible, reduction in the amount smoked will help with complications such as poor wound healing or vascular complications such as blood clots or stroke, or complications such as pneumonia,” says Goodman.
• Improving your leg strength and mobility can also help your recuperation. “Some people who have been immobile for a prolonged period may benefit from formal ‘prehab’ or physical therapy prior to surgery. If you have remained active, then focusing on strengthening your thigh muscles and core can be helpful,” she says.

• Knee replacement can effectively relieve pain and restore mobility for those with severe knee joint damage.
• Proper preparation, rehabilitation, and care after surgery are essential to a successful recovery.
• While the procedure is generally safe, there are risks, including infection and implant complications, that need monitoring.