• Researchers say gaining as little as 11 pounds can increase the odds of knee replacement surgery for both men and women.
  • Experts say they have long suspected a link between weight and knee due to the extra force that additional pounds can place on joints.
  • They say exercise is a good way to lower the risk of knee replacement surgery, especially for people in sedentary jobs.

In what may not be great news for those looking forward to upcoming holiday feasts, new research says gaining even a few pounds can take a toll on an adult’s knees.

Just 11 pounds of extra weight can increase a woman’s odds of needing knee replacement by one-third and a man’s by one-quarter, scientists said last week at the International Congress on Obesity in Melbourne, Australia.

Researchers said even without surgery, the extra pounds can increase knee pain and knee stiffness while decreasing a person’s quality of life and restricting their ability to use their knees properly.

However, a person losing 10 percent or more of their body weight can improve knee arthritis, the researchers said.

Osteoarthritis happens when cartilage cushioning joints wears away over time, allowing bones to rub together, causing pain, swelling, and stiffness.

“In other words, osteoarthritis was more likely to develop with weight gain and to progress more quickly,” said Dr. Anita Wluka, a lead researcher in the study and a professor of rheumatology at Monash University School of Public Health and Preventive Medicine in Australia, said in a statement from the International Congress on Obesity.

The research hasn’t been published yet in a peer-reviewed journal.

Wluka’s team looked at 20 prior studies examining the relationship between weight gain and osteoarthritis.

After combining results from two large studies involving more than 250,000 people, the researchers concluded that weight gain had significant detrimental effects on the knee joint, including visible damage on X-rays.

An 11-pound increase in weight made total knee replacement surgery 35 percent more likely for women and 25 percent for men.

“This is particularly concerning,” Wluka said. “Knee replacements are costly and one in five people are dissatisfied with the results and remain in pain after surgery. Those who remain in pain are more likely to require a second surgery, which is more costly and less likely to control their pain.”

Dr. Benjamin Bengs, an orthopedic surgeon and director of special surgery at the Center for Hip and Knee Replacement at Providence Saint John’s Health Center in California, told Healthline doctors have long believed there’s an association between weight and arthritis.

“Particularly in the load-bearing joint (like the) hip and knee,” Bengs said. “This study adds compelling data in support of this association as well as the increased eventuality of knee replacement surgery.”

Bengs added most people don’t think about how much force their knees see during a normal day.

“We use the term joint reactive forces,” Bengs said. “Knees not only have to withstand the weight of the body but also the force of muscles acting as well as mechanical moments, which can double the amount of load on the knee joint. And that is just for one step. Consider how many steps we take in the course of a day, a year.”

Bengs said adding 11 pounds of a person effectively adds 20 to 30 pounds of force to the joint.

“At some point, cartilage tissue can start to erode, causing arthritis down the road,” Bengs explained.

The good news is that improvement in knee health can happen without most people having to lose massive amounts of weight.

“I have for years suggested to patients that they don’t need to lose 50 pounds because that can be difficult to approach and then no weight gets lost, but rather taking 5 to 10 pounds off can make a difference in the health of the knees,” Dr. Jeffrey Zarin, an orthopedic surgeon at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles, told Healthline.

Zarin said weight isn’t the only factor in knee health. Prior trauma, genetics, and a person’s job – someone who stands or walks all day – also contributes.

“The mystery that still exists is being able to identify definitively why some people are more susceptible to pain and inflammation related to this damage than others,” Zarin said.

Lalitha McSorley, a physiotherapist at Brentwood Physio in Calgary, Canada, told Healthline that sedentary jobs are a big factor.

“Accountants are the perfect example, McSoreley said. “During tax season they often are sitting down for 8 to 12 hours a day. It makes sense that this lifestyle can cause weight gain, but it also creates a lot of tight and angry muscles.”

There are some simple ways to improve knee health, McSoreley said.

“The first and most obvious is exercise. This will help you lose weight and fat, gain muscle mass, and keep your knees healthy,” McSoreley said. “Another thing I recommend patients to do is strengthening/stretching the quadriceps and hamstrings. Isolated quadricep extensions and isolated hamstring curls are my favorite exercises.”

McSorely said tight hips can often “refer pain into the knee.” She recommended using the “clamshell” exercise.

“Begin by lying on a bed on your side. Keep your heels together and your hips stable. Make sure your heels, hips, and shoulders form a straight line,” McSoreley said. “Raise your upper leg three to four inches while maintaining contact with your ankles. Make sure your hips are not rotating. Hold for five seconds. This movement should be slow and controlled. Do this ten times.”

Bengs recommended activities such as elliptical machines and stationary bikes, along with strength training.

Zarin added that using our legs is key to interacting with our physical world.

“In the past, compromise of mobility was more tolerated,” Zarin said. “Once your knees wore out with the ‘curse’ of arthritis, then you ended up in a wheelchair on the porch.”

“Now, as people live longer and stay active for a much greater part of their lives, mobility is crucial,” Zarin said. “Protecting the health of our legs comes from staying fit and flexible as well as keeping our weight down in a healthy range.”