Are you ready for a knee replacement?

If you think you are too young to be one of the 600,000 folks considering having knee replacement this year, you may be surprised.

Close to half of all knee replacements are performed on people ages 45-64, according to data from the Agency for Healthcare Research and Quality in 2012.

Those numbers include total knee replacements, where the entire joint is replaced with metal and plastic, and partial knee replacements (“unicompartmental”), where only parts of the knee are replaced.

“The demographic of knee replacement patients has shifted over the last 15 years, and we see younger patients with end stage osteoarthritis that are candidates for knee replacements — who have exhausted other options and lesser procedures such as injections no longer work,” says Dr. William Robb of the Illinois Bone and Joint Institute.

The cause of this is twofold: increased lifetime participation in sports and activities by baby boomers, particularly women, and the explosion of obesity in our society, which makes symptoms more severe and hastens osteoarthritis, Robb says.

Knees degenerate when cartilage between the bones wears away and bones rub against each other. There are different methods of knee replacement, but according to the American Academy of Orthopaedic Surgeons, knee replacement generally replaces damaged bone with metal and replaces cartilage, including the kneecap, with polyethylene.

Though injections can temporarily ease symptoms, they cannot fix the knee because the disease will continue to progress, Robb says. This is what some younger patients like Jodi Hackendahl, 55, of Libertyville had to come to terms with a few years ago. An avid adult tennis player and childhood gymnast, she had severe knee pain by her early 40s.

“I was scoped at 45 and they told me I would have to have joint replacement by 50. I did it at 52, but I probably waited too long, because by then my leg was bowed and my other knee was going bad,” she says.

She tried various injections, but they didn’t work. She says when she could no longer push her grocery cart through the store because of the pain, she was finally ready.

“My doctor emphasized that knee replacement is something you shouldn’t do unless you are completely ready because the pain is real and the recovery is long and the rehab takes months of commitment,” she says.

“I was hesitant and scared at first. I wasn’t ready to go through the rehab. But my dad’s advice made my choice clear. He said, ‘You can either do it or spend the rest of your life sitting in a chair.’ He knew what he was talking about because he had both his knees replaced in his mid-60s and now enjoys playing golf.”

Hackendahl said it took nine months of tough rehab and exercise to regain full activity, and she had to give up tennis. But now her new knee is pain-free.

She is scheduled to have her other knee replacement in May. “My daughter is getting married a year from this June and I want to do it now and heal and dance at her wedding,” she says.

Only your doctor can determine whether you are eligible for partial knee replacement or full knee replacement, which is the more common procedure but more extreme. There are advantages to seeing a doctor as soon as possible if you have knee pain.

Younger patients worry that if they get a knee replacement at 50, it will have to be redone later. Robb says the percentage of revisions is decreasing modestly over time.

“It was a 10-year technology when it first came out decades ago,” Robb admits. “Now technology and surgical techniques have changed and knee replacements have lifespans of 20-30 years depending on their level of activity.”

He expects advancements to continue, as the AAOS predicts 3 million people per year will be receiving knee replacements by 2030.

Originally published in the Chicago Tribune Prime Time senior living section on May 15, 2015.