When to Return to Play After an ACL Injury

by Mitch Hauschildt, MA, ATC, CSCS

Anterior Cruciate Ligament (ACL) injuries are always a hot topic of discussion in sports medicine circles, not just because of the debilitating nature of the injury, but also because of the high rate of reinjury following an ACL injury.  Of the approximately 250,000 ACL injuries that occur each day in the US, up to 30% of them result in an injury.  Some research demonstrates that within 5 years, up to 50% of patients will sustain a meniscus injury.  Research also demonstrates that athletes who sustain an ACL injury have a very high rate of osteoarthritis in the future.

These crazy high numbers leave those of us who routinely treat ACL injuries wondering what the best plan of care is for these patients.  Recently, I came across a 2016 research study out of the British Journal of Sports Medicine that looked at injury rates following an ACL injury with several different return to sport strategies following an ACL reconstruction.  It is a very interesting article that I suggest you take a look at if you haven’t already read it.

The study examined 106 athletes who had recently undergone ACL reconstruction who had previously participated in level I or II sporting activities at least twice per week.  Seventy-four of the participants returned to level I sports within 2 years of their ACL reconstruction.  Throughout their 2 year recovery process, they tracked their activities, time to return to sport and how they performed in a return to sport evaluation that included isokinetic quad testing, single leg hop tests, and 2 self reported outcomes.

There is a lot of information that can be taken from this study, but the major points that stand out to me are:

• 24 patients sustained a reinjury within the 2 year follow up
• The reinjury rate of those who returned to level 1 sports was 29.7%, resulting in a 4.32 fold increase in risk of injury over those who have not previously sustained an ACL injury
• All 4 patients who returned to their sport within 5 months of surgery sustained a reinjury within 2 months of their return
• For those who returned to sport within 9 months of surgery, for every month they delayed their return resulted in a reinjury reduction of 51%
• There wasn’t a significant difference in reinjury rates after 9 months post op
• Only 18 patients passed their return to sport testing prior to returning to their sport
• Of those 18 who passed their test prior to returning to sport, only 1 patient sustained a reinjury, demonstrating a reduction of 84% in their injury
• Only 66% of patients had quadriceps strength symmetry greater than 90% at the 2 year mark after surgery

As I look at this data, there are several things that I think are important to focus on.

• It struck me that only 18 of the 100 people passed a return to play evaluation prior to them returning to their sport.  When you read the details of the study, there are a number of factors that played into why this occurred within this study, but my experience as I travel the country is that many, if not most, athletes that are performing ACL rehab, are returning to their sport based primarily on timing and not their functional capacity.  This research demonstrates that, while timing is important, it shouldn’t be the only factor.  If you are performing ACL rehab and you aren’t using some sort of a functional return to play evaluation, then you are exposing your patients to a heightened risk of reinjury
• The reinjury rate for those who passed a return to play evaluation and waited until at least 9 months post op experienced a reinjury rate near zero
• What the return to play evaluation consists of might not be as important as the fact that you actually have a return to play criteria.  I personally can point to a lot of holes in their return to play evaluation tool and ways that it can be a lot better, but it is hard to argue with the fact that their reinjury rate with those who passed their return to play prior to returning to their sport.
• It does take a certain amount of time for the graft to fully vascularize and normalize in the knee.  The fact that injury rates significantly drop every month up to the 9 month mark is a big indicator of the fact that we need both a timing component and a functional evaluation component prior to returning to play.  The question becomes, what is the right time frame for return to play?  The goal is to always return to activity as quickly as possible.  But, I will also admit that the older and more mature I get as a clinician, the more conservative I become.  Many physicians have settled into a 6 month minimum time frame, but the reality is that the vast majority of research out there indicates to at least 9-12 months as a minimum for a return to play.
• The fact that their research demonstrates that there is a strength deficit in a large portion of their cohort 2 years later is concerning at best.  Of course, I always ask “why”.  I would say that at the 2 year  point, a strength deficit is primarily neurologically driven.  Meaning, the brain is still feeling that the involved limb is compromised in some capacity, so it isn’t willing to put a lot of effort behind it.  This may be because there is some level instability that continues to be present due to a less than perfect surgical or rehab process.  Or, maybe the rehab process was too focused on a top down approach, and not performing activities that return the body to it’s authentic proprioceptive feedback loop.

The lesson that I have taken from this article is that there clearly needs to be a combination of both time to heal, as well as proof of functional abilities prior to returning an athlete to sport.  This is the approach that we have taken over the years at our institution, but it is always nice to see the research supporting it.

I think we also need to strongly consider holding our patients longer than we would (or they) would like for their own good.  In my world, this is a really difficult conversation with coaches, athletes and parents, because everyone wants to return to their sport as quickly as possible, but if we are truly, authentically interest in the well being of our athletes, we may want to consider waiting a few more months prior to returning to play.  I also know that we can play the argument that if we have a great surgeon and great rehab principles, we can overcome the timeframe, but the truth is that we just don’t fully understand all of the things in play.  And, more than 90% of all ACL reconstructions in the US are performed by surgeons that do less than 10 per year and I suspect the stats are similar for therapists, so the majority of ACL patients are getting less than perfect care.

Finally, we clearly need to monitor our patients long after they’re returned to full activity to make sure they don’t need any fine tuning or maintenance work.  I’m a firm believer that athletes shouldn’t need maintenance work if they are returned to full function with a high quality program focused on the right interventions, but the reality is that the combination of a knee that will never be the same as it was originally with our comfortable lifestyle that promotes poor movement patterns makes it difficult to avoid some sort of maintenance program to optimize long term health.

Grindem H, Snyder-Mackler L, Moksnes H, et al Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study Br J Sports Med 2016;50:804-808.