return to sport after ACL reconstruction

Brandon Schmitt DPT, ATC

      One of the big questions following ACL reconstruction surgery is: when can I go back to play?  A seemingly simple decision on the surface becomes much more challenging in light of the current research.  Only 55% of athletes return to sport, even with full intent to do so, and despite good surgical outcomes.  The reasons range from not trusting the surgical knee to poor self reported outcomes.  Of those who return, they are 15 times more likely to sustain a (second) ACL tear.  Performance can also suffer, with only 66% reaching preinjury level two years out from surgery.
     There are three primary components that need to be considered when making a return to sport decision: biological, physical/functional, and psychological.  From a biological standpoint, the graft needs time to heal and undergo a process called ligamentization in which the graft needs to revascularize and re-innervate.  This process can take twelve months or more to occur based on animal and human studies.  
     The second consideration is the patient's functional performance.  A series of biomechanical studies showed that some athletes who have had surgery showed specific biomechanical deficits, such as knees caving in and stiff knee landing, which were risk factors for future injury.  From these findings a series of tests were designed to test jumping and landing mechanics as well as quadriceps strength.  Hopping and landing mechanics are commonly assessed through a testing battery consisting of single leg hops for both distance and time and compared to the non-surgical leg.  Generally a deficit of less than 10% is required before being cleared to return to sport.  This limb symmetry index, as it's called, is better at ruling out those athletes not yet ready to return to sport versus ruling in those who are ready to return.  While there are some tests designed to look specifically at movement quality, none to date that can be easily done in the clinical setting have been shown to have good predictive value for sustaining another injury.
     The next measure to consider with regards to function is quadriceps strength.  This is most commonly done with an isokinetic dynamometer or with a hand held dynamometer in order to get an object strength measure.  The knee strength on the surgical side is compared to the non-surgical side and a limb-index measure is derived.  Research has shown that for every one percent decrease in this deficit, there is a three percent reduced risk of reinjury to the knee.  At PRO Sports PT we use a biodex unit, which gives the most accurate strength testing measurements.  
     The third component of return to sport is the psychological aspect.  It is not uncommon for an athlete to have some degree of fear and apprehension following ACL surgery.  At PRO Sports we use a special test called the Return to Sports Index (RSI) which measures a patient's emotions, confidence in performance, and and risk appraisal.  This test has been shown to have good reliability, validity, and predictive value. 
    While there is no validated return to sport testing battery with regards to return to sport decision making following ACL reconstruction, we at PRO Sports PT use the most up to date research and our extensive experience, as well as collaborating with the patients and surgeons, in making the decision.  While the decision is not always simple, science and experience can help make the best decision possible.

Sources:

• Ardern CL, Taylor NF, Feller JA, Webster KE. Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors. Br J Sports Med. 2014 Nov 1;48(21):1543-52.
• Grindem H, Snyder-Mackler L, Moksnes H, Engebretsen L, Risberg MA. Simple decision rules can reduce reinjury risk by 84% after ACL reconstruction: the Delaware-Oslo ACL cohort study. British journal of sports medicine. 2016 Jul 1;50(13):804-8.
  
• Hewett TE, Myer GD. Reducing knee and anterior cruciate ligament injuries among female athletes–a systematic review of neuromuscular training interventions. The journal of knee surgery. 2005;18(01):82-8.
  
• McPherson AL, Feller JA, Hewett TE, Webster KE. Smaller change in psychological readiness to return to sport is associated with second anterior cruciate ligament injury among younger patients. The American journal of sports medicine. 2019 Apr;47(5):1209-15.
  
• Paterno MV, Rauh MJ, Schmitt LC, Ford KR, Hewett TE. Incidence of second ACL injuries 2 years after primary ACL reconstruction and return to sport. The American journal of sports medicine. 2014 Jul;42(7):1567-73.
• Scheffler SU, Unterhauser FN, Weiler A. Graft remodeling and ligamentization after cruciate ligament reconstruction. Knee surgery, sports traumatology, arthroscopy. 2008 Sep 1;16(9):834-42.
  
• Webster KE, Hewett TE. What is the evidence for and validity of Return-to-Sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis. Sports Medicine. 2019 Jun 1;49(6):917-29.