Considering the millions of steps the average person takes, it's a wonder more of us don't need new knees at some point in our lives. When you add in all the dancing, running, twisting, turning and plenty of  athletic injuries, it's no surprise that knee replacement surgery is among the most common surgeries.  We have answers for eight frequently asked questions about knee replacement surgery.

1. How common is knee replacement surgery? According to the Agency for Healthcare Research and Quality, more than 600,000 knee replacements are performed each year in the United States, most commonly on patients between ages 50 and 80.

2. Why do people need their knees replaced? The most common reason is because of pain associated with arthritis. Osteoarthritis caused by aging, wear and tear or overuse of the knee joint is the most common source of pain that leads to knee replacement. As cartilage wears out, bones rub against each other and cause inflammation and irritation. Rheumatoid arthritis can also cause joint damage as part of an autoimmune disorder. Post-traumatic arthritis is the result of an injury that damages the joint or cartilage. Sometimes, the pain associated with arthritis of the knee can be treated with medication, support devices, physical therapy and exercise, but when that isn't enough, surgery is recommended.

3. What symptoms would someone feel if they need a new knee? Pain and stiffness when standing, walking or climbing stairs are the most common symptoms, but some people also feel pain when at rest. Joint inflammation or deformity may also lead to knee replacement.

4. How is the knee replaced? The knee is the largest joint in the body formed by the femur (thighbone), tibia (shinbone) and patella (kneecap), which are normally protected by cartilage and covered by a lubricated lining. The American Academy of Orthopedic Surgeons says knee replacement might be more accurately termed  knee "resurfacing" because only the surfaces of the bones are actually replaced. Damaged cartilage and a small amount of bone are removed from the ends of the femur and tibia and replaced with metal components that re-create the joint surface. The kneecap is sometimes resurfaced with a plastic button  and then a plastic spacer is inserted between all metal parts to create a smooth gliding surface.  Surgery takes an hour or two and might be performed using general (you go to sleep) or spinal/epidural regional nerve block anesthesia. 

5. How long will I be in the hospital? You'll probably be in the hospital for a few days to rest, recover and receive physical therapy. You'll start physical therapy exercises the day after surgery and will continue receiving physical therapy throughout your hospital stay and after you go home. You'll receive pain medication in the hospital and during your at-home recovery period.

6. How long before I'm completely recovered? Most patients are walking, exercising lightly and going about their usual routine within three to six weeks after surgery. 

7. Are there any risks to knee replacement surgery? Knee replacement is an overwhelmingly safe surgery. All surgeries however, have risks for infection, pneumonia and blood clots, though hospitals take precautions to prevent these from happening to their patients. In addition, knee replacement patients might experience temporary stiffness in their new joint and they may feel or hear a clicking sound when they bend their knee. This sensation often subsides over time. 

8. How long will my new knee last? On average, a replaced knee joint should last about fifteen years. When your "new" knee wears out, your surgeon can replace it with another one. 

If you're considering knee replacement surgery, consult an orthopedic surgeon who specializes in the procedure and you'll be back on your feet in no time. 


American Academy of Orthopedic Surgeons

Total Knee Replacement

Nathan Wei, MD, Rheumatologist, Arthritis Treatment Center, reviewed this article.