ACL Rehabilitation: Reconstruction and Return to Sport

The term ACL is an abbreviation for the Anterior Cruciate Ligament. The ACL is one of the four main ligaments connecting the thigh bone (femur) to the shin bone (tibia). All four ligaments work together and help provide stability and movement to the knee. The ACL, along with the Posterior Cruciate Ligament (PCL), control the back-and-forth motions of the knee. Along with this task, the ACL also prevents the tibia from sliding out in front of the femur, as well as providing rotational stability to the knee, according to a 2014 paper.

Clearly, this can be a detrimental injury to any athlete, regardless of sport.

What can an ACL injury mean for an athlete?

An ACL injury can threaten an athlete’s career, and returning to the same competitive level is not guaranteed. Outcomes differ between athletes, even as surgery and rehabilitation evolve. This is especially true in sports that require landing and change of direction. A returning athlete may simply be a few steps slower or not be able to perform the same movements again.

Take NBA basketball superstar Derrick Rose for example. D-Rose was one of the most exciting players to watch in his prime. He could jump out of the gym and amazed people with his one-of-a-kind athleticism. He racked up many accomplishments early in his career, including being a three-time all-star before the age of 24, a member of the 2010-2011 All-NBA first team, and being the youngest MVP of all time at age 22 in 2011.

However, at the beginning of the playoffs in 2012, Derrick Rose tore his ACL. He did not play for the rest of the playoffs and sat out the entire next season. His limited return provided a small sample for comparing performance. That comparison cannot isolate the effects of the ACL injury from other factors. He was only able to play 10 games before he tore his meniscus in his other knee.

In those 10 games, he simply could not move as he did pre-injury. His speed, quickness and jumping ability all declined noticeably. While tragic, it was something the medical community studied and used for improvement. Outcomes differ between athletes, even as surgery and rehabilitation evolve.

How are ACL injuries classified?

Injuries to the ACL are rated according to the severity of the injury. A grade-1 sprain stretches the ligament without loss of knee stability, while a grade-2 sprain involves a partial tear and may leave the ligament loose. Rehabilitation and return-to-sport decisions depend on stability, associated injuries, function and sport demands, rather than the injury grade alone. Surgery may be considered, but a complete tear does not automatically make it mandatory; instability, associated injuries and activity goals influence the decision.

A torn ACL is the most severe type of ACL injury. According to a 2014 paper, this typically requires surgery and at least 6 months of rehabilitation with the full process taking over a year. Although recovery is a long process, it is one that has evolved to help more and more athletes return to the professional level. The cited 2012 rehabilitation review described a shift toward earlier motion and individualized progression compared with older protocols.

The cited 2012 review describes programs emphasizing full passive knee extension, early motion and progressive weight bearing, and functional exercises. A 2012 paper stated some doctors begin rehabilitation before surgery if possible. This is to reduce swelling, inflammation, pain, and any other issues that could arise post-surgery.

How do rehabilitation approaches differ?

The process of ACL rehabilitation has been split into two approaches, a conservative/traditional approach, or an accelerated approach. Several studies have considered conservative ACL rehabilitation to be protocols that involve longer immobilization of up to 6 to 8 weeks, followed by progressive weight bearing activities. With a more conservative rehabilitation approach, doctors are allowing the biological factors of tissue healing to determine the timeline for return to the professional level play.

The most obvious upside to the conservative approach being the safety of its successful history. An accelerated approach may start motion and weight-bearing earlier, with restrictions determined by the treating team, the graft and associated injuries. The idea is to restore a patient to preinjury level quicker than any other approach. Progression must account for tissue healing, function and associated injuries; completing a program does not establish that one accelerated approach reduces reinjury risk for every athlete. It is the difference between “slow and steady wins the race” versus getting the hard stuff out of the way and strengthening weakness early on. Overall, both approaches address the same goals through different methods.

The goal is to return a patient to their prior level of function by using movement, weight bearing exercise, and returning full range of motion. Early rehabilitation phases may last several weeks, but the full return-to-sport process is not a 6-to-8-week program. Progress, tissue healing and sport demands guide the return decision. Sports that require more jumping and sudden changes in direction may require a longer rehabilitation program.

It is important that a physical therapist or doctor not rush rehabilitation to the point where a patient is reinjured.

What does ACL reconstruction involve?

A Grade-3 sprain is a complete ACL tear; reconstruction may be recommended, but treatment is selected for the individual rather than dictated by the grade alone. Over the past 30 years, ACL reconstruction surgery has evolved considerably. This is due, in part, to a better understanding of ACL anatomy. In the 1980s, a technique called a free patellar tendon graft was used. This surgery consisted of harvesting the middle third of the patellar tendon and using it as a free graft.

Anatomically, it fits perfectly, but the techniques used to complete the surgery are less than ideal. Patellar tendon grafts can involve donor-site complications, including anterior knee pain, patellar tendinitis and patellar fracture. Doctors also performed a similar surgery, using the Hamstring instead of the patellar tendon. Today, these same methods are used. However, these methods have become much less invasive with the use of arthroscopic procedures. The patellar tendon graft has a long history, while patellar, hamstring and quadriceps tendon grafts remain options selected according to the patient and surgical goals. We now know the extent of the risk and possible damages that may exist with the patellar tendon itself. Rehabilitation techniques are now used to strengthen the patellar tendon, together with the quadriceps. The hamstring is still used to help rebuild the ACL in some patients. Bone blocks at either end are characteristic of a bone–patellar tendon–bone graft. Hamstring grafts are typically soft-tissue grafts fixed within bone tunnels. However, the hamstring tendon itself is much longer than the ACL and is quadrupled into a bundle to resemble the anatomy of the original ligament.

There is also a technique known as the cadaver transplant. An allograft uses donor tissue, with its own risks and suitability considerations to discuss with the surgeon.

What did the source discuss about emerging techniques?

While these may be the main surgeries used for ACL replacement, there are many smaller and more preventive techniques that are also used. Recently, collagen scaffolds are being added to the top of the ligament, in hopes that the healing of the ruptured ACL to the bone will be more effective. Patient selection depends on the particular implant and injury. The FDA’s December 2020 BEAR order included selected patients with complete ACL rupture and a tibial ACL stump, so complete rupture alone does not rule out collagen-assisted repair.

Scientists are also developing permanent reinforcements and true artificial replacements, with varied success. With the development of the COVID-19 mRNA vaccine, the idea of an ACL vaccine may come to light. This would be used to induce muscles to produce specific foreign proteins. In his January 2021 commentary, Kevin Stone speculated about possible future mRNA applications to ligament repair or prevention; this was a future concept, not an established ACL vaccine or treatment.

What affects return to sport after ACL injury?

While new techniques of rehabilitation and surgery may increase an athlete’s odds of returning to play, there are still obstacles in the way of the process being perfected. In fact, the full process will likely never be perfect. An ACL injury, especially a torn ACL will always be detrimental to an athlete physically and mentally. “A big part of the rehabilitation process is teaching the body and mind to function normally with whatever tendon or ligament is used for the repair” according to a 2019 paper. ACL repair is as much of a physical rehabilitation as it is a mental rehabilitation.

Some athletes may never take this full step to returning to the professional level because they are afraid that they may injure or tear their ACL again. Reinjury risk depends on the patient, sport exposure, recovery criteria and follow-up period; it is not a universal 45%-versus-20% split determined solely by whether rehabilitation was completed. But, once an ACL is torn, you are always at risk of tearing it again. In Walker and colleagues’ 2021 survey of 304 adults 1–20 years after ACL reconstruction, 43.8% identified fear of reinjury as a barrier to rehabilitation adherence. That percentage was not a measure of abandoning a professional comeback. Medicine has made great advancements in rehabilitation for ACL injuries. However, there is still more work to be done. Perhaps 20 years in the future, there will not be as great a risk of re-tearing the ACL. There may be new and innovative surgeries that will change the way that we reconstruct any tendon.

Perhaps, one day, tearing an ACL may be as insignificant as stubbing your toe.

References

Advent Health. (2019, November 4). 3 Advancements in ACL Injury Reconstruction. Advent Health Orlando. Retrieved from https://www.adventhealth.com/hospital/adventhealth-orlando/blog/3-advancements-acl-injury-reconstruction#:~:text=A%20torn%20ACL%20can%20heal,transplants%20and%20hamstring%20tendon%20grafts.

American Academy of Orthopaedic Surgeons. (2014, March). Anterior Cruciate Ligament (ACL) Injuries. OrthoInfo. Retrieved from https://orthoinfo.aaos.org/en/diseases–conditions/anterior-cruciate-ligament-acl-injuries/

Chambat, P., Guier, C., Sonnery-Cottet, B., Fayard, J.-M., & Thaunat, M. (2013, February). The evolution of ACL reconstruction over the last fifty years. International Orthopaedics. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3560904/

Luks, H. J. (2021, October 11). Return to Sports After ACL Surgery: 5 Professional Opinions. Howard J. Luks, M.D. Retrieved from https://www.howardluksmd.com/returning-sports-acl-reconstruction-5-professional-opinions/

McMahan, I. (2017, May 11). An ACL injury is no longer a career killer, but can athletes ever truly be the same? The Guardian. Retrieved from https://www.theguardian.com/sport/2017/may/11/acl-injuries-sports-athletes-careers

Sports Reference. (n.d.). Basketball Reference. Retrieved April 18, 2022, from https://www.basketball-reference.com/players/r/rosede01.html

Stone, K. R. (2021, January 31). What is New in the ACL. The Stone Clinic. Retrieved from https://www.stoneclinic.com/blog/what-new-acl-2021

Waldron, K., Brown, M., Calderon, A., & Feldman, M. (2021, August 2). Anterior Cruciate Ligament Rehabilitation and Return to Sport: How Fast Is Too Fast? Science Direct. Retrieved from https://www.sciencedirect.com/science/article/pii/S2666061X21002315

Walker, A., Hing, W., Lorimer, A., & Rathbone, E. (2021). Rehabilitation characteristics and patient barriers to and facilitators of ACL reconstruction rehabilitation: A cross-sectional survey. Science Direct. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S1466853X2100002X

Wilk, K. E., Macrina, L. C., Cain, L., Dugas, J. R., & Andrews, J. R. (2012, March 1). Recent Advances in the Rehabilitation of Anterior Cruciate Ligament Injuries. JOSPT. Retrieved from https://www.jospt.org/doi/10.2519/jospt.2012.3741

American Academy of Orthopaedic Surgeons. (n.d.). ACL Injury: Does It Require Surgery? https://www.orthoinfo.org/treatment/acl-injury-does-it-require-surgery/

U.S. Food and Drug Administration. (2020, December 16). BEAR Implant De Novo classification order, DEN200035. https://www.accessdata.fda.gov/cdrh_docs/pdf20/DEN200035.pdf

Walker, A., Hing, W., Lorimer, A., & Rathbone, E. (2021). Author institution publication record. https://research.bond.edu.au/en/publications/rehabilitation-characteristics-and-patient-barriers-to-and-facili/

Cooke, C. (2021, July 29). Graft Choices for ACL Reconstruction [Detroit Sports Medicine Symposium presentation]. https://foreonline.org/wp-content/uploads/2021/09/9.-Cooke_ACL-Graft-Reconstruction-Options.pdf

Pull Quotes:

“An ACL injury can threaten an athlete’s career, and returning to the same competitive level is not guaranteed.”

“Injuries to the ACL are rated according to the severity of the injury.”

“ACL repair is as much of a physical rehabilitation as it is a mental rehabilitation.”