Prevention of Non-Contact Anterior Cruciate Ligament (ACL) Injuries in Female Athletes
Athletes in sports such as basketball, soccer, tennis, and rugby perform various change of directions of movements including acceleration/deceleration, jumping, and pivoting. Noncontact anterior cruciate ligament (ACL) injuries are common among athletes, particularly when landing from a jump, rapidly stopping or cutting or decelerating with change of direction. Athletes who experience an ACL injury will likely be described as a “pop” or “giving way” sensation with presentation of hemarthroses (redness and swelling) with significant pain within the initial minutes and loss of knee extension.
Figure 1: Anatomy of anterior cruciate ligament (ACL)
Figure 2: Torsion rotation of the knee causing rotation.
Females sustain noncontact ACL injuries 2 – 8x more often than males. This is often attributed to a wider pelvis and increased Q-angle associated with females when compared to males. Increased leg stiffness upon landing coupled with decreased strength in the thigh musculature when compared to males is also likely to contribute to the higher incidence of noncontact ACL injuries in female athletes. These anatomical differences and strength deficits typically cause the knees to come together upon landing (valgus knee position), which may excessively increase the strain on the ligaments and muscles surrounding the knee. 11Knee valgus or medial knee displacement has been referred to as “kissing knees” described as excessive hip adduction and internal rotation during weightbearing exercises such as jumping, squatting, or hopping. Biomechanical variants are often found in these various activities and should be addressed with consideration for what is considered “normal” for the individual.
Figure 3: Q-angle variation males & females
Clinical Assessment of Knee Valgus:
Knee valgus and Trendelenburg (hip drop) can be assessed clinically and in laboratory research setting through various assessments including:
- single leg drop landing
- single leg squat
- single leg balance
- double leg maximal jump
Biomechanical measures including kinematics (peak angles) related to dynamic lower extremity valgus (i.e., any combination of hip adduction/internal rotation, knee abduction and tibial internal rotation) are measured using 3D video analysis has been used in the research setting and the impact of force load through the joint and the impact of injury risk over time.
Role of Strength & Conditioning in Knee Valgus:
Improving hip abductor, hamstring, and gluteus strength to reduce medial knee displacement can be beneficial in optimising performance specific to plyometric sports (i.e., basketball, running, tennis).3
Ideally an ACL prevention program should be initiated at or prior to the onset of puberty for young athletes and encouraged throughout a strength and conditioning program in the pre-season, in order to prevent maladaptive neuromuscular and biomechanical patterns from developing in the first place.8
A good prevention program will include:
- Neuromuscular training/control
- Muscle strengthening
- Education and feedback regarding body mechanics and proper landing patterns in a dynamic atmosphere.
Home Exercises to Strengthen Hip Abductors
Lateral Band Walking
Side-Lying Hip Abduction:
Quadruped Hip Extension
Bulgarian Split Squat
Hip Cable Abduction
Sports Team Pre-Season ACL Prevention Training Program:
The Santa Monica Sports Medicine Research Foundation has implemented the PEP (Prevent Injury and Enhance Performance) program consisting of a warm-up, stretching, strengthening, plyometrics, and sport specific agilities to address potential deficits in strengthening and coordination of stabilizing muscles around the knee joint. (research evidence). The PEP Program can be used by coaches and athletes prior to training.
Programs that begin prior to season enhance the effectiveness of the program, particularly 6 weeks pre-season. It should last 15–20 minutes or longer and be done at least 3 times a week. If the program can be continued throughout the season this may help maintain proper form. It can even be effective as a replacement of the traditional team warm-up.
The Santa Monica Sports Medicine Research PEP Program
The ACL program should incorporate feedback to the athletes regarding landing technique and provide opportunities for the athlete to correct it while practicing proper mechanics. This can involve having a partner athlete, or coaching assistant, provide the feedback, or could include the use of mirrors and video to visually observe both good and bad form. The athlete should be taught to begin and end manoeuvres with proper positioning involving knees and hips being sufficiently flexed, jumping/landing with knees over toes, while avoiding knee valgus upon landing, and remembering to “land softly” (landing with more weight on the forefoot)7
Research by Rodriguez et al. 20189analysed the PEP program to prevent ACL injuries in female collegiate soccer players during an entire season. During the 24 weeks the training program was applied three times a week as a part of the team workouts. Video analysis of dynamic knee valgus alignment and maximal strength of quadriceps, hamstrings and gastrocnemius were evaluated pre- and post-training.
Main findings in this study:
- Significant increase in muscle strength on the quadriceps and hamstrings
- Increased knee functional ability and muscle balance.
- Team injuries through the program did not decrease (i.e., strain or sprain), however, no ACL injuries were registered.
The PEP Program has been successful and implemented at elite levels amongst strength and conditioning programs for sporting teams. Individualised athlete history and performance goals including the rate of progression of a strength and conditioning program should be considered. Physiotherapist can assist in appropriate progression, return to sport, and reaching your sports performance goals.
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- Boham MD, Debeliso M, Harris C, Pfeiffer RP. Quadriceps-to-hamstrings imbalances in female collegiate soccer athletes: Implication for injury. J Athletic Enhancement 2014;3:1-5.
- Fernández-de-las-Peñas, C., & Nijs, J. (2019). Trigger point dry needling for the treatment of myofascial pain syndrome: current perspectives within a pain neuroscience paradigm. Journal of Pain Research, 12, 1899 – 1911.
- 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;33:492–501
- Kobayashi H, Kanamura T, Koshida S, et al. Mechanisms of the anterior cruciate ligament injury in sport activities: A twenty-year clinical research of 1,700 athletes. Journal of Sports Science and Medicine. 2010;9:669–75
- Herrington L. Knee valgus angle during landing tasks in female volleyball and basketball players. J Strength Cond Res. 2011 Jan;25(1):262-6. doi: 10.1519/JSC.0b013e3181b62c77. PMID: 19966588.
- McLean SG, Borotikar B, Lucey SM. Lower limb muscle pre-motor time measures during a choice reaction task associate with knee abduction loads during dynamic single leg landings. Clin Biomech (Bristol, Avon) 2010;25:563–9
- Munro A, Herrington L, Comfort P. Comparision of landing knee valgus angle between female basketball and football athletes: Possible implications for anterior cruciate ligament and patellofemoral joint injury rates. Phys Ther Sport 2012;13:259-64.
- Otsuki, R., Benoit, D., Hirose, N., & Fukubayashi, T. (2021). Effects of an Injury Prevention Program on Anterior Cruciate Ligament Injury Risk Factors in Adolescent Females at Different Stages of Maturation. Journal of sports science & medicine, 20(2), 365–372. https://doi.org/10.52082/jssm.2021.365
- Rodríguez C, Echegoyen S, Aoyama T. The effects of “Prevent Injury and Enhance Performance Program” in a female soccer team. J Sports Med Phys Fitness. 2018 May;58(5):659-663. doi: 10.23736/S0022-4707.17.07024-4. Epub 2017 Feb 21. PMID: 28222578.
- Renstrom P, Ljungqvist A, Arendt E, et al. Non-contact ACL injuries in female athletes: an International Olympic Committee current concepts statement. Br J Sports Med. 2008;42:394–412. doi: 10.1136/bjsm.2008.048934.
- Sands W, Wurth, S Hewitt J. Basics of Strength and Conditioning Manual. National Strength and Conditioning Association, 2012;63
- Willson JD, Davis IS. Utility of the frontal plane projection angle in females with patellofemoral pain. J Orthop Sports Phys Ther. 2008;38:606–15.