The Problems with Knee Replacements

Replacements Don't Last Forever

Traditionally, knee replacements were performed in patients over 60 years of age. However, in the last 20 years, an increasing number of patients younger than 60 years old have been receiving knee replacements (Jain, Kurtz). The estimated expected life of a replacement knee ranges from 10 to 30 years, although some fail sooner. About 10% of patients have to have the replacement joint replaced after 10 years (10 year survivorship of 90%) and 20% by 20 years (20 year survivorship of 80%).If a patient is 60 years old when they have their knee replaced, the odds of them dying before their joint wears out is fairly high. However, if a patient is only 50 years old when they have their initial knee replacement, they are more likely to outlive the lifespan of their replacement joint and need to have additional surgery.

Increased use of the prosthetic joint will cause it to wear out faster. Younger patients who expect to be physically active put more wear and tear on the joint and therefore are more likely to wear the joint out more quickly. One study by Rand showed that the 10 year survivorship of patients over 70 years old was 94%, for patients ages 56-70 years old the 10 year survivorship was 89% and for those under 55 years old the 10 year survivorship was only 83%.

Surgical Complications

Knee replacement surgery is a major surgery and therefore has potential complications. The most common serious complications from this surgery are infection, wound healing problems, deep-vein thrombosis (DVT) and pulmonary embolism. Serious infections of the newly replaced joint can require additional surgery and even removal of the replacement joint. Even once these infections heal, they may result in damage to the new joint that leads to ongoing problems with pain and loosening of the joint. A study by Frosch showed that 23.6% knee replacement surgeries had some complication and that a revision operation was required in 5.6% of the cases. The most common complication in this study was delayed wound healing.

Long Term Satisfaction

Success rates of knee replacement surgery are usually measured by how many patients have revisions of the initial surgery. But many patients who have had joint replacement end up with joints that still cause them pain and problems, but live with the symptoms instead of having a revision surgery performed.

Studies that have looked at patients' expectations for knee replacement surgery have found that patients expect to be pain free and have great mobility of their knee joint after surgery. They expect to be able to return to all their old activities at the level of participation they had before they began having knee problems.

The reality is different than patient expect. A study by Mannion showed that 85% of patients expected to be pain-free after surgery, but only 43% were. 52% of patients expected to by unlimited in their usual activities, but only 20% actually were. When this group of patients was asked if they could go back in time and make the decision over again to do the surgery would they do it? - 73.9% said yes definitely, 18.9% said yes probably, 6.3% said no probably not, and 0.9% said no definitely not.

Another study by Nilsdotter found that 98% of patients expected much less or less pain postoperatively. At 1 year, 93% were experiencing much less or less pain, but by 5 years only 63% were experiencing much less or less pain than before surgery. In this same group, 96% expected their daily activity function to be better and 72% expected their sports and recreation function to be better. Daily activity levels were better for 90% at one year and 61% at 5 years, while sports and recreation function was better for only 25% at 1 year and 32% at 5 years.

Age also plays a role in functional results. A study by Elson and Brenkel showed that patients younger than 60 years old at the time of surgery were more than twice as likely to report poor pain scores at 5 years after the surgery as patient who were over 60 years old. A study by Singh found that patients younger than 60 years old were more likely to have moderate to severe pain 2 years after surgery than patients who were 61 to 70 years old.

A study by Price in patients under 60 years old found the 12 year survival rate was 82% when you considered revision surgery a failure. But when you looked at functional outcome or pain as the endpoint, the survival rate at 12 years was only 59%.

Obesity and Knee Replacement

Obesity is a rising problem in the United States and the world. Patients who are obese put more stress on their knees and are more likely to have knee problems. Obesity creates several problems for patients who have knee replacement surgery. A study by Samson showed that obese patients have a higher rate of knee replacement surgical complications than non-obese patients. They found a 3 to 9 times higher rate of infection in the obese patients. Additionally, they found that although obese patients might expect that their mobility would increase after surgery and that therefore they might lose weight, in fact, these patients did not tend to lose weight after surgery thereby continuing to put additional stress on their new joint.

Obese patients wear out their replacement joints more quickly and are more likely to need revision surgery. A study by Amin showed that obese patients had a higher risk of complications than non-obese patients (32% of patients compared to 0%) and a higher failure rate at 3 years (27.7% of patients compared to 2.4%). Another study by Vazquez-Vela Johnson looked at patients 10 years after surgery. The overall survival rate was 96.8% at 14 years. However, the worst performing groups was a group of obese men less than 60 years old who had a 10-year survival rate of only 35.7%.

Revision Surgery for Failed Knee Joint Replacement

When a joint replacement wears out or loosens, the patient has 2 options; live with the resulting pain and decrease in function or replace the failed joint for a new one (revision surgery). Revision surgery is a more complicated and extensive surgery than an initial knee replacement. Usually more bone needs to be removed and a larger area needs to be replaced with artificial parts. Because this surgery is usually longer and more complicated, there is a higher level of complications from the surgery. A study by Khatod found a 7.7% complication rate for original knee replacement surgery and a 10% complication rate for revisions. Infection is much more common in revision surgery and a study by Mortazavi found that it was the major cause of failure of revision joints. Additionally, they found that by 5 years, 18.3% of the revisions had failed, requiring yet another revision (compare this to the 10% failure rate at 10 years for initial knee replacement). 83% of the failures occurred in the first 2 years after the revision surgery.

Even when the revision is successful, patients do not tend to do as well as after the first knee replacement. A study by Greidanus showed that revision patients had a poorer quality of life in all measures compared to patients after an initial knee replacement.


In the right patient, a knee replacement can supply relief from pain and improved mobility. However, for some patients, especially younger patients, knee replacement may not the best first choice. In many cases, patients can find improvement in their symptoms without joint replacement. Using these alternatives, younger patients may defer the need for a joint replacement until much older. Joint replacements in older patients are more likely to result in good outcomes and less likely to need revision surgery in the future. Older patients who use alternatives to knee replacement may find that they never end up needing a replacement at all.

The main alternatives to joint replacement fall into two major categories: nonoperative treatments and surgical treatments. Please explore both of these sections to see the options that are available.