Two new studies found that exercise may be a factor in recovering from a total knee replacement (total knee arthroplasty or TKA) and knee osteoarthritis (OA). One study involving a progressive quadriceps strengthening program after total knee replacement found that it enhanced clinical improvement almost to the level of healthy older adults. The other study, the first to examine the relationship between four components of physical activity and the incidence of knee OA in older adults, found that certain types of activities were linked to an increased risk of the disease. The studies were published in the February issue of Arthritis Care & Research (http://www3.interscience.wiley.com/journal/77005015/home).
Nearly half a million total knee replacements are performed each year in the U.S. to treat severe knee OA, which is on the rise due to an increase in the elderly and overweight populations. Although knee replacement improves function, patients continue to have impaired quadriceps strength and function for activities such as walking and climbing stairs, which remain below those of healthy people of the same age. Rehabilitation targeting these areas has not been studied well and is not routinely prescribed.
A randomized controlled trial led by Lynn Snyder-Mackler of the University of Delaware and funded by the National Institutes of Health involved 200 patients who had undergone a knee replacement and 41 patients who received conventional standard of care (inpatient rehabilitation and home physical therapy). The 200 patients received six weeks of progressive strength training two or three times a week that targeted knee extension, range of motion, kneecap mobility, quadriceps strength, pain control and gait. Half of this group also received neuromuscular electrical stimulation (NMES).
The results showed that those who did the strength training program had significant improvements in quadriceps strength and muscle activation, functional performance and self-reported function and that they also demonstrated substantially greater quadriceps strength and functional performance after 12 months than the standard of care group. There were no significant differences between the group that just did exercise and the group that did exercise plus NMES.
"Our data suggest that individuals who do not undertake an intensive rehabilitation program following TKA are clearly at a disadvantage," the authors state. They point out that quadriceps strength is related to functional performance and was the single greatest predictor of function for activities such as rising from a chair or climbing stairs. Functional performance typically peaks about three years following surgery and slowly declines in the following 10 years. "Failing to obtain adequate functional recovery may accelerate functional decline and predispose these individuals to an early loss of functional independence as they age," the authors conclude.
Another study published in the same issue and led by Led by Marjolein Visser of VU University Medical Center in Amsterdam involved almost 1,700 men and women ages 55 to 85 years old of the LASA study that were assessed over a 12-year period for knee OA. Their physical activity was evaluated with a questionnaire that included information on frequency and duration of physical activity over a two-week period. Intensity, mechanical strain, turning action and muscle strength scores were created for each activity.
During the follow-up period, 28 percent of participants developed knee OA. Activities with low muscle strength (such as light household work) or high mechanical strain (such as dancing or tennis) were associated with an increased risk of knee OA, even after adjusting for demographics, health, and early life/current physical activity, as well as the other components of physical activity.
The study did not find an association between the level of overweight and mechanical strain in the incidence of knee OA. "This finding could indicate that the higher risk of knee OA in obese persons may be explained by factors other than increased mechanical strain, and higher levels of physical activity may not negatively affect knee health in heavier respondents," the authors state.
The authors caution that before these results can be translated into advice for health professionals on daily activities for older adults, further studies need to be conducted to clarify the optimal amount of daily activity necessary for healthy joints for each component of physical activity.
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