About 200,000 anterior cruciate ligament (ACL)
injuries happen each year in the United States, and half of those
injuries are surgically repaired, according to the American Academy
of Orthopaedic Surgeons. Usually, surgeons replace the torn ligament
with a grafted replacement.
Osteoarthritis occurs when protective cartilage on the ends of bones
wears down, and it can't be reversed. Researchers have known that
reconstructed knees get osteoarthritis more often than healthy
knees, but how much the risk increases was hard to determine.
"The time interval between the ACL injury and osteoarthritis is
long, usually more than five years," Dr. Bjorn Barenius said.
Barenius worked on the study at the Karolinska Institutet in
"Ten to fifteen years after the injury is often quoted as a time
when you can expect signs of osteoarthritis," he told Reuters Health
in an email.
But osteoarthritis can be influenced by many factors, like
sustaining more injuries or gaining weight, which might make
arthritis hit earlier, he said.
For the new study, radiologists examined X-rays of both knees of
people who'd had ACL surgery at least 14 years earlier.
Based on the expert assessments, 57 percent of ACL-reconstructed
knees had arthritis, compared to 18 percent of healthy knees,
according to the results published in The American Journal of Sports
How long people had waited between the knee injury and surgery
didn't seem to change their likelihood of having arthritis.
Since there was no comparison group of people who had ACL injuries
that were not repaired with surgery, it's impossible to say if the
surgery or the injury itself increased arthritis risk, Barenius
Surgery may help keep the knee from giving way during sports but not
restore all of its normal mechanics, he said.
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When the ACL is compromised, the knee joint essentially gets
looser, so bones put more pressure on cartilage, which then wears
away quicker, said Yasin Dhaher. He studies orthopedic injuries at
Northwestern University in Evanston, Illinois.
"But ... it is very rare that you would have an isolated ACL
injury," he said.
"The injury is usually complex and includes meniscal tear," which
exposes more cartilage to higher wear and tear, Dhaher said. He was
not involved in the new study.
For athletes who have ACL reconstruction, osteoarthritis may start
to affect their performance many years down the line, but they will
have more immediate issues to deal with first, he said.
"For most sports and most athletes, the instability of the ACL injury
will affect their sport more than the future prospect of
osteoarthritis," he said.
As far as what patients can do to try to ward off arthritis,
Barenius suggests maintaining a healthy weight.
Rehabilitation and exercise can help too, Dhaher said. Without
surgery, most badly injured knees do develop arthritis, he said.
The American Journal of Sports Medicine, online March 18, 2014.
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