Fall sports are underway. Invariably, you’re going to hear about the dreaded ACL tear, that puts an end to an athletes season. I decided it was important to share some information regarding ACL injury prevention since there are still many misconceptions regarding the topic.
WHAT IS AN ACL INJURY?
- The ACL (anterior cruciate ligament) is one of the four main ligaments of the knee. An ACL rupture is a major concern for athletes, especially for those who participate in contact sports, as it leads to short term disability and long term negative impacts to the knee joint.1 The knee joint moves in three planes: forward/back, side-to-side, and rotation, and ligament rupture can occur when the knee moves beyond the normal range of these planes of movement. Research shows that long term negative impacts of an ACL rupture produces “significant pain, functional limitations, and radiographic signs of knee osteoarthritis within 12–20 years of the injury.”2-4 Therefore, ACL education and participation in a research-based ACL injury prevention program is essential for athletes.
- Female athletes are at a greater risk than males. Female athletes who participate in sports requiring jumping and pivoting incur ACL injuries at a 2- to 10-fold greater rate than male athletes participating in the same sports.1 In a study by Ford KR, Myer GD, Schmitt LC, et al., post-pubescent females were found to “rely more heavily on quadriceps muscles relative to hamstrings muscles with incremental increases in landing intensities.”5 Female athletes were also found to demonstrate greater hip movement, decreased hip muscle recruitment and increased knee to hip moment ratios with landing when compared to their male counterparts.1
- Previous ACL Injury. Once an athlete sustains an ACL injury, they are at a significantly higher risk of sustaining another, either on the same or opposite side.1,6,7 This could be due to a variety of factors. The athlete could have underlying musculoskeletal issues that contributed to the initial ACL rupture that weren’t addressed in the rehabilitation phase of recovery. Also, ACL reconstructed athletes often demonstrate a favoritism toward their opposite limb, even up to 2 years post-operatively. These asymmetries play a significant factor in the risk of re-rupture.1
- Joint Laxity. Though there is limited literature about genetic risk factors, there may be a link between joint laxity and ACL injury. Collagen disorders such as Marfan’s Syndrome and Ehlers Danlos are examples of congenital disorders that influence joint laxity.1
PREVENTION CONSIDERATIONS: Inexpensive clinical assessment tools such as the Y Balance test and functional hop tests can reliably assess risk factors associated with potential ACL injury. Additionally, a helpful study by Timothy Hewett et al., found several components are essential in a prevention program: age, biomechanics, compliance, dosage, feedback and exercise variety.1
- Age: Younger athletes who participate in early prevention exercises have shown a decrease in ACL injuries.8-10
- Biomechanics: Faulty body alignment, especially during landing activities, correlates with increased stress on the ACL. Increased knee valgus (knee moving inward compared to the foot) is the strongest risk factor for ACL injury.1,11-14
- Compliance: Adherence to a research-based exercise prevention program is essential to the successful prevention of ACL injury. Research has shown that even a compliance rate of 66% can reduce ACL injuries by 82%. However, when the compliance rate drops to less than 66%, the ACL injury rate decreases to just 44%.15,16
- Dosage: To attain full effectiveness, an ACL prevention program should ideally be performed 20-30 mins several times per week, initiated pre-season and continued throughout the season.17,18
- Feedback: Feedback from a coach or video accelerates the learning process for the athlete learning how to avoid stressful movements to the ACL (especially knee valgus, as mentioned above).10,19-22
- Exercise Variety: The prevention program must contain a mix of plyometrics, balance and strengthening activities in order to achieve full effectiveness at ACL injury prevention.1,23-28
Exercise Recommendations: This is not an exhaustive list — merely a list of some exercise ideas to get you started. Feel free to improvise and be creative! Note: some of the exercises utilize a bosu ball. You can perform these activities on an uneven surface if you don’t have access to one.
- Squat jumps
- High knee jumps/box jumps
- Power skips
- Power jacks
- Power push-ups
- Split squats
- Lunge to power knee drive
- Plank Jumping mountain climbers
- Medicine ball slams
- Lateral skater jumps
- Quad eccentric lower progressing to theraband resistance
- BOSU squats both legs progressing to single limb
- Dumbell Deadlift
- Sidestepping with theraband progressing to lateral shuffling
- Landing from raised surface both legs progressing to single limb
- A and B-Skip progressions
- Sustained squatting and eccentric quad strengthening, progressing to sustained squat with front/back/sideways movement
- Lateral stepping with passing
- Squat/pass drills
- BOSU squats with option to add weight
- Pistol squats on BOSU
- Single leg dead lift
- Reverse lunge from BOSU
- Plank with alternating leg lifts
SUMMARY: In summary, the research overwhelmingly shows that exercise variety in an ACL prevention program is KEY in preventing ACL injuries and enhancing performance! Perform a variety of plyometrics, strength and balance exercises at least 20-30 mins, several times per week for the best chance at preventing an ACL injury.
About the Author: Brandi Arndt, MPT, is a former athlete herself. Like many physical therapists, Brandi suffered through injuries and rehab in order to keep playing. She received her Masters in Physical Therapy from Maryville University in 2008 and has spent a majority of her career working with children and athletes who’ve undergone complex orthopedic procedures. She practices in North County (Hazelwood, MO)
- Hewett, Timothy E., et al. “Mechanisms, Prediction, and Prevention of ACL Injuries: Cut Risk with Three Sharpened and Validated Tools.” Journal of Orthopaedic Research, vol. 34, no. 11, 2016, pp. 1843–1855., doi:10.1002/jor.23414.
- Lohmander LS, Ostenberg A, Englund M, et al. High prevalence of knee osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury. Arthritis Rheum. 2004;50:3145–3152.
- Myklebust G, Bahr R. Return to play guidelines after anterior cruciate ligament surgery. Br J Sports Med. 2005;39:127–131.
- von Porat A, Roos EM, Roos H. High prevalence of osteoarthritis 14 years after an anterior cruciate ligament tear in male soccer players: a study of radiographic and patient relevant outcomes. Ann Rheum Dis. 2004;63:269–273.
- Ford KR, Myer GD, Schmitt LC, et al. Preferential quadriceps activation in female athletes with incremental increases in landing intensity. J Appl Biomech. 2011;27:215–222.
- Pinczewski LA, Lyman J, Salmon LJ, et al. A 10-year comparison of anterior cruciate ligament reconstructions with hamstring tendon and patellar tendon autograft: a controlled, prospective trial. Am J Sports Med. 2007;35:564–574.
- Salmon L, Russell V, Musgrove T, et al. Incidence and risk factors for graft rupture and contralateral rupture after anterior cruciate ligament reconstruction. Arthroscopy. 2005;21:948–957.
- Mandelbaum BR, Silvers HJ, Watanabe D, et al. Effectiveness of a neuromuscular and proprioceptive training program in preventing anterior cruciate ligament injuries in female athletes: two-year follow-up. Am J Sports Med. 2005;33:1003–1010. doi: 10.1177/0363546504272261.
- Myer GD, Sugimoto D, Thomas S, et al. The influence of age on the effectiveness of neuromuscular training to reduce anterior cruciate ligament injury in female athletes: a meta-analysis. Am J Sports Med. 2013;41(1):203–215. doi: 10.1177/0363546512460637.Wright RW, Dunn WR, Amendola A, et al. Risk of tearing the intact anterior cruciate ligament in the contra-lateral knee and rupturing the anterior cruciate ligament graft during the first 2 years after anterior cruciate ligament reconstruction: a prospective MOON cohort study. Am J Sports Med. 2007;35:1131–1134.
- Steffen K, Myklebust G, Olsen OE, et al. Preventing injuries in female youth football—a cluster-randomized controlled trial. Scand J Med Sci Sports. 2008;18(5):605–614. doi: 10.1111/j.1600-0838.2007.00703.x.
- Hewett TE, Myer GD. The mechanistic connection between the trunk, knee, and ACL injury. Exerc Sport Sci Rev. 2011;39(4):161–166.
- Hewett TE, Myer GD, Ford KR, et al. Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: a prospective study. Am J Sports Med. 2005;33(4):492–501. doi: 10.1177/0363546504269591.
- Hewett TE, Torg JS, Boden BP. Video analysis of trunk and knee motion during non-contact anterior cruciate ligament injury in female athletes: lateral trunk and knee abduction motion are combined components of the injury mechanism. Br J Sports Med. 2009;43(6):417–422. doi: 10.1136/bjsm.2009.059162.