Research shows that building strength before a knee replacement leads to better outcomes.
For the burgeoning numbers of Americans facing a knee replacement, what they do before surgery may be just as important as what they do after. Emerging science shows that prehab—building strength before surgery—leads to better outcomes.
More than one million knee replacements are performed in the U.S. every year, and 3.48 million a year are expected by 2030, the American Academy of Orthopedic Surgeons says. The most rapid increase is in the 45-to-64 age group, according to the National Center for Health Statistics.
Exercise, or mechanical loading as scientists call it, improves stem cells that stimulate tissue regrowth and increase blood supply. Having those stem cells and tissues primed helps healing, says Fabrisia Ambrosio, associate director of physical medicine and rehabilitation at the University of Pittsburgh Medical Center.
Dr. Ambrosio’s work, still in the early stages, applies regenerative-biology research to prehab recommendations. Fitness can dictate success after surgery, she says, but research is underway to pinpoint the optimal amount, duration, type and intensity of exercise.
An earlier study by researchers at Beth Israel Deaconess Medical Center and Harvard Medical School found knee- and hip-replacement patients who did strength, aerobic and flexibility exercise in water or on land for six weeks before surgery reduced their chances of needing inpatient rehab by 27%. Those who exercised showed an increase in muscle strength of 18% to 20%, says Daniel Rooks, then assistant medical professor at Harvard, now an executive director of musculoskeletal translational medicine at Novartis Institutes for BioMedical Research in Cambridge, Mass.
“Muscles can act as shock absorbers” for joints, says Vonda Wright, orthopedic surgeon and chief of Northside Hospital Sports Medicine in Atlanta. “The more lean muscle mass you have, the better,” she says.
Prehab is particularly useful when knees are weak and have limited range of motion, says Patrick Horst, an orthopedic surgeon and assistant professor at University of Minnesota Medical School. Even 15 minutes daily of therapist-directed exercise for two months before surgery is beneficial, he says. “Greatly improved range of motion before leads to easier recovery and greater range of motion after,” Dr. Horst he says.
Robin Robertson, a 57-year-old road- and mountain-bike racer in Bellingham, Wash., trained for her surgery date as if it were a coming race. Already fit by most standards, she added strength training six weeks before surgery. She worked with a specialized trainer to design a program to increase strength without further damaging her knee. “With any strength move, form is key,” Ms. Robertson says.
Her improved muscle tone was a factor in the decision to perform her total knee replacement as an outpatient procedure, says Michael A. Thorpe, the orthopedic surgeon who did the surgery.
Comparing her subsequent rehab to what the hospital manual told her to expect, Ms. Robertson says she progressed twice as fast as average.
While the worst thing anyone with degenerative changes in the knee can do is to remain sedentary, some types of exercises can make the situation worse, so it’s important to choose wisely, says Stephen Sylvester, doctor of physical therapy and associate professor of health and human performance at Palm Beach Atlantic University in Florida.
“Avoid any exercises that increase the compressive forces on the knee, such as a step class or high-impact aerobics,” Dr. Sylvester says, adding that bicycling and in-water exercises are usually fine. When it comes to strength training, doing more repetitions with low resistance is generally safest for damaged joints, he says, but patients should consult a physical therapist about their specific situations. The key, he says, is for patients to do what they can without bringing on more pain and swelling.
