Patient education: Knee replacement (The Basics)

What is knee replacement? — 

This is surgery to replace part or all of the knee joint with artificial, or "prosthetic," parts.

The knee joint is made up of the:

●Lower part of the thigh bone (femur)

●Kneecap (patella)

●Top part of the shinbone (tibia)

In between the bones is a rubbery material called cartilage. Normally, the cartilage lets the bones slide over each other without causing pain.

When a person has problems with their knee joint, it can cause pain, swelling, or stiffness. Different conditions can cause knee problems. One of the most common causes is osteoarthritis, a type of arthritis that often comes with age (figure 1). When osteoarthritis happens, the cartilage in the joint begins to break down.

Knee replacement is a treatment that can reduce knee pain and improve how the knee works.

Knee replacement is an "open" surgery. This means the doctor makes a cut ("incision") in the skin so they can see directly inside the body to do the surgery. They usually make the incision down the center of the front of the knee. They make it as small as possible to limit injury to the muscles and other tissues around the knee.

How do I prepare for knee replacement? — 

The doctor or nurse will tell you if you need to do anything special to prepare.

Before the procedure, your doctor will do an exam and make sure you are healthy enough to have surgery. They might send you to get tests, such as:

●Blood tests

●X-rays

●Electrocardiogram ("ECG") – This measures the electrical activity in the heart.

Your doctor will also ask about your "health history." This involves asking about any health problems you have or had in the past, past surgeries, and any medicines you take. Tell them about:

●Any medicines you are taking – This includes prescription and "over-the-counter" medicines, plus any herbal supplements. It helps to write down and bring a list of your medicines, or bring a bag with all your medicines with you. You might have to stop certain medicines for a short time before surgery.

●Any allergies you have

●Any infections – If there is infection anywhere in your body, it needs to be treated completely before any prosthetic parts are put in.

●Any bleeding problems you have – Certain medicines, including some herbs and supplements, can increase the risk of bleeding. Some health conditions also increase this risk.

Before surgery, the doctor might want you to:

●Learn about exercises you can do before and after surgery.

●Learn to use crutches, a walker, or a cane.

●Quit smoking, if you smoke. Your doctor or nurse can help. It takes longer for bones to heal if you smoke. Smoking also increases the risk of problems after surgery.

●Try to lose weight, if you have excess body weight.

You will also get information about:

●Eating and drinking before the procedure – You might need to "fast" before the procedure. This means not eating or drinking anything for a period of time. Or you might be allowed to have liquids until a short time before the procedure. Whether you need to fast, and for how long, depends on the procedure.

●What help you will need when you go home – For example, you will need someone else to bring you home or stay with you for some time while you recover.

Ask the doctor or nurse if you have questions or if there is anything you do not understand.

What happens during knee replacement? — 

When it is time for the procedure:

●You will get an "IV," which is a thin tube that goes into a vein. This can be used to give you fluids and medicines.

●You will get anesthesia medicines. This is to make sure you do not feel pain during the procedure. Types of anesthesia include:

•Regional – This blocks pain in 1 area of your body, such as an arm, a leg, or the lower half of your body. Common types include "spinal" and "epidural" blocks. For these, a doctor injects medicine to numb the nerves in or near your spine. They can also do a "nerve block" to numb your knee area. This can help control pain after surgery.

If you get regional anesthesia, you will probably also get "sedative" medicines to make you relax and feel sleepy.

•General – This makes you unconscious so you can't feel, see, or hear anything during the procedure. You might get a breathing tube to help you breathe.

●You will get medicines to help prevent infection and control pain after the procedure.

●The doctors and nurses will monitor your breathing, blood pressure, and heart rate during the procedure.

●The doctor will make an incision, usually down the center of the front of your knee. Then, they will remove the damaged parts, and replace them with artificial, or "prosthetic," parts. These can be made out of metal, ceramic, or plastic (figure 2).

●The doctor will close your incision and cover it with clean bandages.

●The procedure usually takes about 2 hours.

What happens after knee replacement? — 

You will be taken to a recovery room. The staff will watch you closely as your anesthesia wears off. You might be able to go home a few hours later. Or you might need to spend 1 or more nights in the hospital or go to a "rehabilitation" ("rehab") facility.

As you recover:

●You might feel groggy or confused for a short time. You might also feel nauseous or vomit. The doctor or nurse can give you medicine to help with this.

●If you had a breathing tube, you might have a sore throat. This usually gets better quickly.

●You will get medicine to help with pain.

●The staff will help you get out of bed. A physical therapist will help you stand and start to walk soon.

●You might get X-rays so the doctor can look at your knee. You might also get blood tests.

●You might have to wear special boots or stockings to help prevent blood clots in your legs. You will get medicine to help prevent blood clots as well.

●When you are ready to eat, you will start with clear liquids. Then, you can start eating as you are able. You might feel better if you start with bland foods.

What are the risks of knee replacement? — 

Your doctor will talk to you about all the possible risks, and answer your questions. Possible risks include:

●Blood clot

●Infection

●The kneecap moving out of place

●Broken bone

●Nerve or blood vessel damage

●Reduced blood flow to the leg

●Bleeding

●The prosthesis wearing out, loosening, or breaking

●The wound not healing properly

●Joint stiffness

●A reaction to the material in the prosthesis

What else should I know? — 

Before you go home from the hospital, make sure you know what problems to look out for and when to call the doctor. Make sure you understand your doctor's or nurse's instructions. Ask questions about anything you do not understand.

When you go home, you will get instructions about physical therapy and specific exercises to do. These will help build your muscle strength and flexibility. Physical therapy is a very important part of the recovery process.

More on this topic

Patient education: Knee replacement – Discharge instructions (The Basics)
Patient education: Deciding to have a knee replacement (The Basics)
Patient education: Knee pain (The Basics)
Patient education: Knee arthroscopy (The Basics)
Patient education: Osteoarthritis (The Basics)
Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)
Patient education: How to use crutches (The Basics)
Patient education: How to use a walker (The Basics)

Patient education: Total knee replacement (Beyond the Basics)
Patient education: Knee pain (Beyond the Basics)
Patient education: Joint infection (Beyond the Basics)
Patient education: Deep vein thrombosis (DVT) (Beyond the Basics)