Most athletes who undergo ACL reconstruction surgery do return to some form of sport, but only 55 percent will return to competitive level sports, an updated review suggests.

About 200,000 anterior cruciate ligament (ACL) knee injuries happen each year in the United States, and half of those injuries are surgically repaired, according to the American Academy of Orthopaedic Surgeons. Surgeons usually replace the torn ligament with a grafted replacement.

The authors reviewed the topic in 2010 and found that less than half of patients returned to competitive level sport, but since then, reporting on whether or not athletes return to play after surgery has increased, they write in the British Journal of Sports Medicine.

“I think we used to presume that everyone returned to their sport after surgery, especially since one of the main reasons why people have surgery is because they want to return to sport,” said lead author Clare L. Ardern. “But clearly these results show that this is not the case.”

“I think this is lower than what we previously assumed was the case, but having said that, this doesn’t mean that people stopped playing sport altogether,” said Ardern, of the School of Allied Health in the Faculty of Health Sciences at La Trobe University in Bundoora, Australia.

“Some people may have changed the sport they played, but we were not able to measure this in our study,” she told Reuters Health by email.

Ardern and her team reviewed 69 new articles on ACL surgery and return to play published between April 2010 and November 2013.

Of the 7,556 patients in total, 81 percent returned to some level of sport after surgery, while 65 percent returned to pre-injury level and 55 percent returned to competitive level sports.

This is an area where sports medicine specialists strive to improve,” said Gregory D. Myer, director of the Human Performance Laboratory at Cincinnati Children's Hospital Medical Center in Ohio.

“Our mission in sports medicine is to get everyone back to their pre-injury activity levels regardless of the injury,” said Myer, who was not involved in the review. “A 55 percent success rate is certainly below the standards we aim to achieve.”

Younger players and men were more likely to return to sport than older players or women, the researchers found.

Elite athletes were about six times more likely to return to competitive sport than non-elite athletes.

Not surprisingly, better physical function after surgery increased the chances of returning to sports. Patients who were able to hop the same distance on each leg after surgery were more likely to play competitively again.

“These results are only generalizable if you were an athlete prior to sustaining the injury,” Myer said.

Psychological function seemed to make a difference too.

Patients who had more fear of injuring themselves again and less psychological readiness to play were less likely to return to pre-injury level sport.

Psychological factors may be modifiable, unlike gender or age, which makes mental readiness to play an important factor for doctors to consider, the authors write.

“More and more we are recognizing that physical and mental recovery is important to maximize the chances of returning to sport after surgery,” Ardern said. “This means that patients and their physical therapists need to make sure they also address both aspects.”

Patients should make sure they really understand what surgery and rehabilitation involves, and work with their physical therapist to set realistic goals, she said.

“Sometimes it can be useful to talk to teammates or friends who have had an ACL injury and made a successful return to sport about what it took and what to expect,” Ardern said. “In a team environment, if there are teammates with ACL injuries, it can be helpful for them to be paired together for rehabilitation to motivate each other.”