Repeat offender: torn anterior cruciate ligament (ACL)

Anterior cruciate ligament (ACL) injury, long the bread and butter of therapists and the bane of athletes, especially females, is undergoing scrutiny because of the high rate of repeated injuries. As many as 25% of athletes suffer a repeated ACL tear and up to 55% of those who suffer an initial tear never return to their previous level of play (1,2). Researchers debate why the high prevalence of repeat injuries. One theory is that something besides the ACL controls tibial stability. Alicia Filley explores recent thinking on the anteriolateral ligament in the first of her series on ACL injuries. The ALL is an extra capsular ligament thought to contribute to limiting tibial external rotation (see figure 1). Some theorize that the prevalence of arthroscopic surgeries means that repairs are directed into the joint at the exclusion of extra-capsular structures like the ALL. This would explain why structurally sound ACL repairs have such high rates of post-repair laxity and repeated injury.

Figure 1: Knee joint anterolateral complex anatomy

Another theory as to the high rate of recurrence of injury is that athletes return to play too soon or without adequate rehabilitation. In the second part of her series, Filley highlights some essentials of post-ACL repair rehab as well as explores the fundamentals of conservative management. One of the challenges in the acute phase post ACL injury, is activation of the vastus medialis obliquus (VMO) and attainment of full knee extension. In a recent publication, French physicians demonstrate an exercise approach that uses fatigue to inhibit the hamstring, and then facilitates contraction of the VMO with resulting terminal knee extension (see figures 2 and 3 and video 1).  See full article here (4).

Figure 2: Hamstring fatigue

Figure 3: VMO faciliation

Video 1: Novel approach to facilitation of VMO

Another study, just released ahead of print, found that poor static balance, particularly postural sway in healthy female subjects, as measured by the amount that the center of gravity of the foot moves per second, was a risk factor for non-contact ACL injuries (4). If a risk factor in healthy subjects, how much more can one assume decreased balance is a risk factor in athletes post tear or repair? Therefore, to prevent re-injury, perturbation drills and proprioceptive training, such as those recommended by ACL rehab specialist Mick Hughes, are crucial in post ACL tear rehab before returning athletes to the playing field (see figure 4).

Figure 4: Perturbation drills

Used with permission, @MickWHughes

References

1. Clin Sports Med. 2018 Jan;37(1):33-40
2. EFORT Open Rev. 2017;2:410-20
3. Arthrosc Tech. 2018 Jun; 7(6): e601–e605.
4. Arch Orthop Trauma Surg. 2018 Jul 19. [Epub ahead of print]