How successful is knee replacement surgery?

Knee replacement has become the most common form of joint replacement surgery. In 2010 over 721,000 such procedures were performed in the United States.1 Between 1991 and 2010, the incidence of knee replacements increased by over 161%, due partly to improvements in the science of knee replacement implants, experience of surgeons, and the growing population of knee replacement patients.2 Although public perception can be influenced by negative advertising and press, the fact is that knee replacement surgery is one of the most successful surgical procedures performed today and patient perception is by and large positive.3

Success rates

Success rates and quality of life improvements for knee replacement patients are reliably very high. Nine out of 10 knee replacement patients experience an immediate relief from knee pain, and 95% report they are satisfied with their procedure.5 Approximately 90% of replacement knee joints last 10 years, while 80% are good for 20+ years, depending on patient health and activity levels. Outcomes vary from patient to patient.4

Who gets a knee replacement?

Most knee replacement patients are over 60 years of age (52.66%), but certain factors can necessitate knee replacement in younger people and there is a growing incidence of patients in their 50s, 40s and even 30s who have had successful knee replacements.1 The largest contributing factor to needing a knee replacement is advanced arthritis, however other conditions such as osteonecrosis (reduced blood supply to bone causing bone death and pain), and injuries (trauma from accidents or sports injuries) may lead to breakdown of the knee joint and create the need for knee replacement surgery.4

More about reasons for knee replacement >>

Rehabilitation as a factor in success

While knee replacement surgery is largely very successful, the success of the procedure is partly due to the rehabilitation period that follows the surgery. For you to expect a good result from knee replacement surgery, you must be an active rehab participant. The importance of this cannot be underestimated!

Rehabilitation after knee replacement begins almost immediately. You will work with a physical therapist as soon as the surgical procedure has been performed. The emphasis in the early stages of rehab is to maintain motion of the knee replacement and to ensure that you can walk safely. The body reacts to surgery by making scar tissue, and you may never recover normal motion if you do not focus on bending and straightening your knee replacement according to your doctor’s and physical therapist’s instructions.6

Your physical therapist will work with you to develop a rehabilitation plan of action that you can continue with at home or in a local gym. During this recovery and rehab period, it is important to follow the physical therapist’s instructions carefully and not over work your new knee joint or surrounding muscles and tissues while they are healing and becoming stronger.

More about recovering from knee replacement surgery >>

More about exercise and physical therapy following knee replacement >>

What results can you expect from your new knee?

While successful knee replacement gives excellent pain relief, it does not give you a normal knee. Many patients are pain-free, but some still may have occasional aches and a feeling that it’s not their “own” joint. Most patients can get back to activities; however, high impact activities or running after knee replacement is not recommended. For the first six to eight weeks you should be especially careful not to pivot or twist the joint, and to keep the knee as straight as possible while lying in bed. Kneeling and squatting also should be avoided for this period after knee replacement surgery.7

More about recovering from knee replacement >>

When is revision surgery necessary?

“Revision” surgery is procedure that removes and replaces the original implant, usually due to a complication from the initial knee replacement. The vast majority of knee replacements (96.3%) require no revision within 18 months of the original surgery.5 Those that do require revision (3.7%) are usually due to infection or mechanical complications of the implant. After 10 years the incidents of revision surgery increase (12%) usually due to long term wear and loosening of the implant.5

What can you do to avoid the need for revision surgery?

  • Follow your doctor’s recommendations for recovery post-surgery
  • Learn and do the recovery physical therapy exercises as directed
  • Use your new knee but do not overdo it or put unnecessary stress on the joint

Fortunately, many of the contributing factors to knee replacement revisions can be prevented by mindful attention to your new joint and avoiding activities that may over-stress the implant and surrounding muscles.

With any surgical procedure there are risks of complications. Some of the reported complications with knee replacement surgery include:5

  • Mechanical complication of the implant (4.3%)
  • Blood clots: deep vein thrombosis, pulmonary embolis (3.9%)
  • Cardiac complications (3.2%)
  • Post-operative infection (1.8%)

Although the incidence of complications is very low compared to the success rate, it is important that you consider your own level of risk and discuss that with your doctor. For example, an overweight 65 year old who has led a mostly sedentary lifestyle and has a family history of osteoporosis (brittle bones) is likely to have a higher risk of complications post-surgery than an individual with strong bone density and a more active lifestyle. Genetics, family history, and lifestyle play a large part in the success rate of any surgery.

More about possible knee replacement surgery complications >>

What about implant recalls and lawsuits?

There have been some (2010-2012) recalls and lawsuits concerning joint replacement implants and procedures, and they represent a very small portion of the total implant population. Media and negative advertising, especially by law firms to promote lawsuits, get far more attention than successful surgeries.

Joint replacement implant manufacturers are continually improving and evolving their products to better serve the patients who receive and use them, and as mentioned above success rates of the surgery remain exceptionally high.

One manufacturer, Zimmer Biomet, has begun standing behind their implants by offering a warranty on their partial knee replacement system that will pay expenses associated with revision surgery should it be needed.

Surgical procedures are also continually being evaluated and updated. Most joint replacement manufacturers offer specialized training in the proper implementation of their products to surgeons all over the world. That is why it’s important to discuss with your surgeon what types of implants they have had the most experience and success with, and if they have participated in any specialized training provided by the manufacturer of those implants.


  1. HCUPnet, a service of the US Department of Health & Human Services (
  2. Shaw, Gina, WebMD feature, “Hip and Knee Replacements on the Rise” (
  3. Mann, Denise, WebMD Health News, “Knee Replacement Surgery is ‘Durable, Reliable, and Successful” (
  4. Cedars-Sinai Orthopedic Center (
  5. Fawzi, Natalie, and Krucik, George, MD, “Knee Replacement Stastics Infographic” (
  6. Cluett, Jonathan M.D., “Considering Knee Replacement Surgery?” (
  7. Knee Replacement Surgery for Arthritis (

image credit: Steven Depolo

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