You rely on your knees every time you stand, sit or walk. So when disease or injury causes pain or limits movement in these joints, it affects you every day.
Treatment for a knee problem may include rest, medication, walking supports, physical therapy, cortisone injections or surgery. If these therapies or a less-invasive surgery isn't enough, your doctor may recommend a total knee replacement, or total knee arthroplasty. 
This surgery helps restore function and relieve pain in people of varying ages, from teens who have juvenile arthritis to older adults with degenerative conditions, according to the <a href="[BASEDOMAIN]/healthinfo/bouncelink.aspx?shortcut=ortho" target="_blank">American Academy of Orthopaedic Surgeons</a> (AAOS). 
The inside story 
Three bones meet at the knee joint: the lower end of the thigh bone (femur), the upper end of the shin bone (tibia) and the knee cap (patella). 
The surfaces where these bones meet are covered with cartilage, a material that cushions the bones and helps them slide against each other smoothly. 
When cartilage is damaged by disease or injury, the bones can rub against each other, causing pain and making movement difficult. The most common causes of damage include osteoarthritis, rheumatoid arthritis and arthritis from a severe injury. 
Knee replacement surgery replaces the damaged parts of the knee joint with metal and plastic. 
The right knee for the job 
An orthopedic evaluation will help determine if surgery is the best treatment option for you. 
According to the AAOS, the evaluation may include: 
<ul>
 <li>A medical history to determine your general health and the extent of your pain and disability. </li>
 <li>A physical exam to check your knee motion, stability, strength and overall leg alignment. </li>
 <li>X-rays to assess the extent of damage and deformity in your knee. </li>
 <li>In some cases, blood tests or an MRI (magnetic resonance imaging) will be done to check the condition of the bones and soft tissues in your knee. </li>
</ul>
Your doctor will also talk to you about the risks and benefits of the surgery.
Planning for surgery 
Before surgery, you should tell your doctor about all medications you're taking, including over-the-counter medicines and herbal supplements. You may also want to take care of any major dental work because of a slight risk that the knee implant could get infected if you have dental work done after surgery. 
For several weeks after surgery, you'll need help with cooking, shopping, bathing and doing laundry, according to the AAOS. If getting help at home is difficult, you may want to arrange to stay in an extended-care facility for a little while after the surgery.
At home you may want to install: 
<ul>
 <li>Safety bars in your shower or bath. </li>
 <li>Handrails along stairways. </li>
 <li>A toilet-seat riser with arms. </li>
 <li>A shower chair or bench. </li>
</ul>
You should also have a stable chair with a firm seat and back, armrests and a footstool.
The AAOS also recommends removing all loose carpets and cords. If you have a multi-level home, you should arrange for a temporary living space on a single floor so you don't have to use stairs right away. 
The procedure 
Before surgery, a doctor will talk to you about your options for anesthesia, most often general or spinal. General anesthesia puts you to sleep for the whole operation. Spinal anesthesia numbs only your legs. 
During the procedure, your surgeon will remove the damaged cartilage and bone and position the parts of the new joint so that your knee functions properly. According to the AAOS, the procedure itself will probably take about one to two hours, and you may spend another several hours in the recovery room after surgery. 
After surgery 
You may have some pain after surgery, but it can be managed with medication. You may also need to take medicines to help prevent blood clots and infections. You'll stay in the hospital for several days, depending on how quickly you heal. 
How much function and strength you regain in the replaced knee is partly up to you. For the best results, follow your doctor's and physical therapist's instructions on wound care, exercises and activity after surgery. 
You should notice a gradual improvement over time, according to the AAOS. 
The results 
According to the AAOS, more than 90% of modern total knee replacements are still working 15 years after the surgery. 
Most people can straighten the replaced knee almost completely and bend it enough to go up and down stairs and get in and out of a car. You should also be able to walk, swim, golf, hike and ride a bicycle. 
High-impact activities aren't recommended for anyone who's had knee replacement surgery, according to the AAOS. Examples include jogging, contact sports, jumping sports and high-impact aerobics. 
Reviewed 3/20/2024
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Sources
<ul>
 <li>American Academy of Orthopaedic Surgeons. "Activities After Total Knee Replacement." <a target="_blank" href="https://orthoinfo.aaos.org/en/recovery/activities-after-knee-replacement">https://orthoinfo.aaos.org/en/recovery/activities-after-knee-replacement</a>.</li>
 <li>American Academy of Orthopaedic Surgeons. "Total Knee Replacement." <a target="_blank" href="https://orthoinfo.aaos.org/en/treatment/total-knee-replacement">https://orthoinfo.aaos.org/en/treatment/total-knee-replacement</a>.</li>
</ul>
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A guide to total knee replacement

This surgery replaces virtually every component of the knee joint with metal and plastic parts. After several months of recovery, most people find it's easier and less painful to move around than it was before the surgery.