ACL Re-Injury: When Should Athletes Return to Sport?

There’s nothing worse than injuring yourself during the season. It’s no fun being stuck on the sideline, but proper healing is important. After an injury athletes are always eager to get to sport, but does what happens if they go back too soon? Athletes post anterior cruciate ligament (ACL) surgeries often ask, “How likely am I to suffer another ACL injury if I have already undergone one reconstruction?” A research article by Beischer et al. gives us the answer to this commonly asked question. The article reports that according to research, 1 in 4 athletes less than 25 years old suffer a second ACL injury after returning to sport. In this post we’re going to dive a little deeper into the correlation between returning to sport too soon and ACL re-injury.

Beischer Et Al.

Beischer et al. investigated the relationship of sustaining a second ACL injury and time of returning to sport. The study looked at the symmetry of muscle function and symmetry of quadriceps strength at the time of return to sport. This study was a prospective cohort study meaning, the researchers follow alike groups of people over period of time that differs in certain characteristics. In this case, there were 2 groups. One group that returned to sports before and one that returned after 9 months post surgery.

Who Was Studied?

There were 159 athletes (64% females, 36% males) included in the study, age range 15-30 years old. The athletes all participated in knee strenuous sports such as soccer, handball, volleyball, football and several others. Those who were excluded were athletes who had more than 1 subsequent ACL injury, who had complications during the muscle function tests such as, muscle strains or knee pain and those who just did not respond to the study specific questionnaire.

All athletes completed 2 strength tests, testing their quad and hamstring strength, as well as 3 single-leg hop tests (vertical hop, hop for distance, and side hop). In order to determine right and left leg as symmetrical in function, an athlete had to have a limb symmetry index (LSI) of 90% or more, in all 5 tests mentioned earlier.


Out of all participants:

  • 63% of athletes returned to sport between 7 and 11 months after ACL reconstruction
  • 24% achieved symmetrical muscle function between the right and left leg before returning to sport
  • 11% athletes sustained a new ACL injury (10 graft ruptures and 8 contralateral ACL ruptures) occurring between 9-36 months after the initial reconstruction.
  • 33 athletes returned to sport before 9 months and 30% of those suffered new injury

The study found that achieving symmetrical muscle function in 5 tests or symmetry in quadriceps strength was not associated with new ACL injury. The muscle symmetry findings contradicted previous research that has supported a relationship between muscle function and new knee injury. In conclusion, those who returned to sport earlier than 9 months after the surgery, had an approximately 3-7 time higher rate of new ACL injury compared to those who returned 9 months or later.

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Please, call us to schedule you evaluation at one of BeneFIT’s locations in Bridgewater (908.203.5200) or Chester (908.879.5700)  with one of our highly-trained Doctors of Physical Therapy!