Who knew? New knees need quick action

When it comes to knee-replacement surgery, she who hesitates may be making a big mistake. Research at the University indicates that women wait longer to pursue knee-replacement surgery than men do, endangering their quality of life.

By postponing surgery until they can no longer stand the pain, these women may also risk putting their mobility on hold indefinitely, according to Lynn Snyder-Mackler, Distinguished Alumni Professor in the Department of Physical Therapy and a certified sports physical therapist and athletic trainer.

“Doctors typically tell patients to wait to have knee replacements until they just can’t stand the pain any longer,” Snyder-Mackler says. “Our research shows that’s bad advice—and worse for women than it is for men—because your level of function going into surgery generally dictates your level of function after surgery.”

Snyder-Mackler led the research team for the study, which was funded by a grant of more than $1.1 million from the National Institutes of Health. Her collaborators included Stephanie Petterson, AS ’02M, ’06PhD, who also was a postdoctoral researcher in physical therapy at UD and now is a senior lecturer at the University of East London, and Drs. Leo Raisis and Alex Bodenstab, orthopedic surgeons at First State Orthopaedics in Newark, Del.

At the University’s Physical Therapy Clinic on campus, 221 candidates for total knee replacements, a group consisting of 95 men and 126 women with osteoarthritis, were evaluated and compared with 44 healthy men and women who matched them in gender, age and body-mass index. Each subject took part in a series of standard physical tests such as walking for six minutes and stair climbing.

The strength of the participants’ quadriceps, the major thigh muscle that extends and straightens the knee, and range of motion of the knee also were assessed at the clinic, which handles more than 300 visits by patients each week.

While the men generally were stronger and had more knee function than the women, the test results showed a much greater degree of physical disability in the female knee-replacement candidates compared with the males in the group.

“The women afflicted with osteoarthritis were at a much more advanced stage than the men with the disease,” Snyder-Mackler says. “The women all had painful end-stage osteoarthritis, where the cushion of cartilage padding the knee bones has completely deteriorated and you basically have bone hitting against bone.”

She says there may be a number of reasons that women wait so long before pursuing surgery. Perhaps women can bear pain better than men, or a woman’s world increasingly revolves around the home as she ages, or it could be that women are just trying to follow doctor’s orders.

“Osteoarthritis of the knee is the most common cause of disability among Americans. It’s a disease of age that affects more women than men on a 60-40 basis,” Snyder-Mackler says.

“Physicians generally have advised patients to wait as long as they can before pursuing knee replacements, with the thinking that it is a once-in-a-lifetime surgery that should last an average of 20 years. However, delaying surgery can limit the quality of life of patients because how they function before surgery indicates their performance afterward.”

Women need to become more educated about the risks and benefits of knee-replacement surgery, she says, and heed the warning signs of serious problems.

“When you feel profound buckling and weakness in your knee when climbing stairs, that is a major problem. You compensate; eventually, you may come downstairs only once a day,” Snyder-Mackler says. “As a result, you become sedentary, and that’s not good for your health. Earlier intervention can help preserve your mobility and quality of life.”

The research is one of two UD studies led by Snyder-Mackler and reported recently in the Journal of Bone and Joint Surgery.

In a related study, she worked with Dan Ramsey, assistant professor of exercise and nutrition science at the University of Buffalo, and UD colleagues Kristin Briem, physical therapist, and Dr. Michael Axe, clinical professor of physical therapy, to determine the effectiveness of “unloader” knee braces in reducing pain and improving function.

The research, which also was supported by the National Institutes of Health, showed that these braces actually promote pain relief by diminishing muscle contractions rather than by “unloading” or separating the joints. Such knee braces may provide an inexpensive treatment option for some osteoarthritis patients.

Snyder-Mackler says she has always been interested in research on knee injuries and in providing solutions to improve people’s lives.

“I’ve always had a burning desire to bring evidence to bear on clinical problems. That’s always been really important to me,” she says. “There are real people at the end of the research loop—patients, physical therapists and physicians, and the patients’ families.”

—Tracey Bryant