Writing in Journal of Clinical Investigation, the team behind the small scale study revealed how 20 grams of essential amino acids taken twice daily for a week before and for two weeks after knee-replacement surgeries helped 16 patients with a mean age 69 recover faster and with much less muscle atrophy than a control group who received a placebo.
Led by Professor Hans Dreyer from the University of Oregon, USA, the researchers suggested that the approach could spell relief and speed up recovery for a growing population of aging adults who face total knee-replacements because of loss of mobility and pain problems.
"We've learned that the essential amino acids were able to mitigate the amount of muscle loss," said Dreyer. "The functional measures that we looked at - getting up out of a chair, going up a flight of stairs and going back down the stairs - were all back to baseline in the treatment group, whereas in the placebo group those times on all of the functional measures were much longer."
"That suggests that this is a means at which we can accelerate functional recovery."
The essential amino acid supplement contained rapidly absorbed raw amino acids - a mix of histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine and valine.
The team noted that muscle wastage (atrophy) in the quadriceps, has been a long-running problem following knee-replacement surgeries.
In the study, 12 members of a control group receiving 40 grams per day of non-essential amino acid supplement (a placebo) averaged an 18.4% loss in quadriceps muscle mass in their operated leg six weeks after surgery.
Those given the essential amino acid (EAA) supplement averaged a 6.2% loss, the team said.
Atrophy in non-operative legs was about 50% of that in the operative leg in both groups, they added.
Dr Brian Jewett explained that a faster recovery is a big plus for knee-replacement patients, because most of them have been dealing with pain for a long time.
"Walking and being physically active are difficult for them pre-operatively and post-operatively, but for different reasons," he said. "Surgery removes the pre-operative pain and disability, and physical therapy helps restore range of motion and strength post-operatively. EAA appear to facilitate this process, presumably by reducing muscle loss."
"In the end, if I can get my patients able to go up and down stairs and get up from a chair sooner, then this is much better for their overall health, and we saw this occur 6 weeks after surgery in the EAA group," said Jewett.
"This also suggests a durability-of-treatment effect because EAA treatment was stopped two weeks after surgery and functional mobility measures were recorded four weeks later, or six weeks after."
Six weeks after surgery, patients in the control group took 32% more time to rise from a chair, walk three meters, turn around and sit back down, compared to before surgery. Patients receiving essential amino acids took about the same amount of time as before surgery.
"Essential amino acids supplementation represents a major advancement on the rehabilitation front," said Jewett. "I think about EAA supplementation as a potentially low-cost opportunity to jump-start the rehab process."