A new study finds that partial knee replacement surgery, where only the damaged parts of the knee get swapped out while the healthy ligaments remain intact, is much safer than total knee replacement. Both types of surgeries are most often given to people who suffer from severe osteoarthritis in the knee. But when it comes to the risks involved, they are not equal. Even though patients who have partial operations are 40 percent more likely to need more follow-up surgery than those who undergo total reconstruction, doctors from Oxford University in England have discovered some potentially scary outcomes linked to total knee replacements.

According to the study, people who have a total knee replacement are twice as prone to blood clots, deep infection, or heart attack and are three times more likely to have a stroke than partial-replacement recipients. And although the risk of death following any type of knee surgery is small, you are four times more likely to die within the first month of a total reconstruction and have a 15 percent greater chance of dying in the next eight years than someone who has a partial operation.

"Total knee replacement is a bigger, longer operation with more blood loss, more bone resection, and significantly more damage to the soft-tissue envelope that surrounds the knee," says study coauthor and surgeon Dr. Alexander Liddle. "The entire knee is exposed, and the ligaments have to be 'balanced' by releasing them at their insertions. This causes more blood loss, which puts strain on the heart, and makes blood clots more likely. This translates into a much higher rate of heart attack, stroke, and death after total knee replacement. We believe that the higher mortality rate is simply a reflection of the greater likelihood of complications that put stress on the body."

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There are definite uncertainties with partial knee replacements too. Any time a surgeon cuts you open, there's some degree of risk. "As a knee surgeon, I would advise all patients to be cautious about exposing themselves to any surgery," Liddle says. "Knee replacement is a major operation with inherent risks, and it is not to be undertaken lightly, particularly if you have pre-existing medical problems." He says certain diseases can make knee surgeries even riskier. And then there's the fact that a much higher percentage of partial replacements wind up requiring a second surgery down the road.

Weighing out the many risks and benefits of both types of operations has surgeons divided. "The choice of total or partial knee replacement is subject to debate amongst knee surgeons," Liddle says. "We already know that people recover more quickly, have better functional outcomes, are more likely to return to work or sports, and have a more 'normal' knee after partial knee replacement compared to total. This is probably because the anterior cruciate ligament (ACL), which is vital to normal knee function, is retained in partial knee replacement. However, surgeons are often not keen to offer it due to the well-reported higher reoperation rate."

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But there is some good news here: Liddle says partial knee replacements are becoming more effective. "This study has shown that the difference in reoperation rates is smaller than seen in previous studies," he says. Total knee replacement surgeries are also improving, which is minimizing some of the associated risks, according to Daniel Riddle, a physical therapy professor at Virginia Commonwealth University who has also extensively studied knee surgeries. "Total knee replacement procedures have improved, [knee] implants have improved, and impatient and outpatient care post-surgery have greatly improved," he says. "Surgical outcomes are now much better, and so the risks have dropped."

The bottom line: Talk extensively with your doctor if you have arthritis in your knee and are considering a replacement. Riddle says surgery should not be the go-to option for relieving knee pain and regaining joint mobility. It can be highly effective, but there are less invasive methods to ease arthritis symptoms that you should try first "The most effective strategy is long-term weight loss," says Riddle, since carrying excess poundage puts undo pressure on the knees. "The average body-mass index of knee surgery recipients is around 30, so half of these patients are obese. Weight loss and lifestyle modification are so important for reducing the need for surgery."