ACL reconstruction is one of the most common sports-related orthopaedic surgeries in the U.S. and is regularly advised for individuals who aim to return to unrestricted sports activity. Many of these athletes expect they will return to sports, without limitations, by the following competitive season. Unfortunately, outcomes following ACL reconstruction are largely varied; less than half of athletes return to their previous level of competition. For those who do resume sports activities, up to one in four will experience a second ACL rupture, and as one would expect, outcomes following revision ACL reconstructions are even worse than primary injuries.

As clinicians, this information probably feels downright scary, and at this point you’re probably hoping for some good news.

So here’s the upside: risk for second injury may be just as modifiable as primary ACL injury risk. Paterno and colleagues from Cincinnati Children’s Hospital screened 56 ACL-reconstructed athletes with a drop vertical jump task and single limb stability, then prospectively followed 56 ACL-reconstructed athletes for one year after their medical clearance to return to sport to determine the biomechanical and neuromuscular characteristics predictive of second ACL injury (read the article here). Transverse plane hip moments and frontal plane knee moments during landing, sagittal plane knee moments at initial contact and deficits in single limb postural stability combined for a highly accurate second injury prediction model. Each of these factors is likely modifiable with targeted neuromuscular training. And how do we know that?

Good question.

Primary and second injury risk profiles share excessive plane motion at the knee, and primary prevention models inclusive of three-dimensional plyometric movements with an emphasis on correct technique effectively reduce primary injury incidence between 52 and 85%! (see Sadoghi 2012). Rehabilitation for athletes who have torn their ACL has progressed quite a bit in the last twenty years (as in, no more six weeks of immobilization….), but only recently have we begun to understand the importance of restoring normal mechanics and function to BOTH limbs. Dynamic movement asymmetries are highly prevalent in the months and years following ACL reconstruction, and, by Paterno’s 2010 data set, many of these factors significantly influence second injury risk. Contralateral limb injury risk also appears to be higher than that of graft rupture, and is significantly higher in female athletes (Paterno 2012). It would seem reasonable, therefore, that a neuromuscular training program targeted to known second injury risk factors may have a similar injury-reducing effect seen with primary prevention programs.

In our recent current concepts article in AJSM (read here), we propose the fundamental components of successful second ACL injury prevention programs which focus on movement re-education during highly dynamic, sports-related tasks. There are really three main take-home points:

  • Neuromuscular deficits persist DESPITE surgical reconstruction
  • Some of these deficits can increase risk for a second ACL injury
  • Targeted neuromuscular training may reduce injury risk and injury incidence.

The case is made for objective determination of functional recovery prior to releasing your athletes to sport (Read: time isn’t everything. Look at this AJSM article – Myer 2012 – for more on why you shouldn’t let yourself or your athlete be a slave to the clock!). Expert clinical research groups in the field advocate the use of a battery of clinical tests and measures to determine readiness to return to sport. Everything from objective strength and hop testing, to self-report outcome tools…. combinations of dual and single-leg tasks…. you name it. It all adds up to a more accurate, descriptive clinical picture of your patient.

Finally, every clinician who works regularly with athletes knows that successful return to play isn’t all based on physical performance. Fear of re-injury is commonly reported in athletes who have not fully returned to their sports activity (McCullough 2012). It is unknown how intensive, late-phase rehabilitation and return to sport training may affect the psychological factors associated with medical clearance. But it does seems probable, however, that the implementation of dynamic, progressive training, which emphasizes technique with faded feedback, concurrent with objective measures of performance, may actually reduce fear in these athletes and enhance their safe return to sport.

Bottom line: we have a lot of work to do to figure out how to reduce the risk of second ACL injuries, so until we find the Holy Grail of prevention programs, here are a few guidelines to remember:

  1. Address movement flaws early – practicing terrible technique = perfecting terrible technique.
  2. Rigorously asses the abilities of your athletes with a battery of clinical tests – if you don’t, game-time will!
  3. Test, progress, ….and re-test. Don’t assume the program worked – TEST it!
  4. Follow-up. Athletes can get off track when they leave your watchful eye. A few repeat testing sessions following discharge from your care can help them document their progress and help you catch impairments.

— Written by Stephanie Di Stasi, PT, OCS, PhD

Staff Physical Therapist
Research Associate
OSU Sports Medicine & Rehabilitation, OSU Campus