Your knee has been hurting for a while, and it hurts bad. You've had trouble sleeping. It may be hard to bathe, to do normal chores like wash the car, or even be comfortable on the job. You may have severe arthritis in your knee, and if so there's a good chance you need a knee replacement.

So, what is a knee replacement?

Knee replacements are usually done in people age 60 and older. If you need one, you probably have severe arthritis that limits your daily life.

During knee joint replacement, your surgeon will remove damaged cartilage and bone from the knee joint. The surgeon then puts man-made pieces, called prostheses, in their place. The lower end of the thigh bone, also called the femur, is usually replaced with a metal part. The part that replaces the upper end of the shin bone, the tibia, is usually made from metal and a strong plastic. The piece that replaces the back side of your kneecap, or patella, is usually made from a strong plastic.

You shouldn't feel any pain during surgery because you will have medicine to make you fall asleep. The surgeon will make a cut over your knee to open it up. The cut is usually eight to ten inches long. Your surgeon will move your kneecap out of the way, then cut the ends of your thigh bone and shin bone to fit the replacement part. The surgeon will then cut the underside of your kneecap and prepare it for the new pieces that will attach there. The surgeon then fastens the two parts of the prosthesis to your bones (the upper end of the shin bone and the lower end of the thigh bone). Then the parts are attached to the underside of your kneecap using a special cement. The surgery usually takes a couple hours.

After surgery, you will probably stay in the hospital for three to five days. As soon as the first day after surgery, you will be asked to start moving and walking around with a walker, crutches, or a cane. You will likely need physical therapy to strengthen your new joint after your operation. Some people need a short stay in a rehabilitation center after they leave the hospital. At the rehab center, you will learn how to safely do your daily activities on your own. Full recovery can take three months to a year.

Your new knee should last for 15 years or maybe even 20. And in the mean time, your new knee should allow you to resume your daily activities once you have learned to move around. Most or all of your pain and stiffness should go away.