2Objectives Brief understanding of prevalence and risks of ACL injuries Understand knee mechanics and importance in protecting the ACLFamiliar with the components of ACL prevention program
3What is the ACL anyway? ACL – anterior cruciate ligament 1 of 4 ligaments in the knee jointProvide stability by limiting the tibia (lower leg bone) from moving forward in relation to the femur (upper leg bone)Limits rotation of the knee joint
4ACL injuries/tears Contact vs. non-contact ~80% non-contact (soccer, basketball, skiing, etc.)~20% contact (football, ice hockey)Non-contact – usually with landing, rapidly stopping, cutting or change in directionAltered biomechanical and neuromuscular patternsFemale athletes have 3.5 x risk of non-contact injury compared to males
6Prevalence of ACL injury Roughly 250,000 ACL Tears per year in the U.S.$20,000+ per reconstruction + rehabilitation$5 billion annual cost6-12 months away from sportHigh rate of re-injury upon return
7BracingFollowing ACL repair and appropriate rehab – generally not used during sportno scientific evidence that a brace is needed after successful reconstruction and rehab.1May use if have ACL tear without surgical interventionBracing supports the muscles and ligaments at the knee region – typically with rehab and sport specific exercises the brace will not be needed and may actually cause the knee to become weaker as the body relies on the brace. Bracing needs to be used until athletes achieve optimal outcomes (good strength, stability, etc).
8ACL Injury Prevention Program: Basic Components Warm–Up (~2 min): increase core temp, increase heart rate, and circulation throughout the musculatureStretching (~2 min): either dynamic (stretching while moving) or static (stationary/traditional stretching)Strengthening (~4min): focus on the hip region and the thigh regionsPlyometrics (~4 min): jumping, landing, ballistic movementsAgility (~4 min): cutting, changing directions
9ACL Prevention Program Goal: decrease the number of ACL tearsImprove neuromuscular control and train proper movement patternsGain biomechanical efficiency and accuracy of movementEnhance dynamic strength and muscle endurance of the trunk, hip and knee15-minute training session that replaces the traditional warm-up of practiceEducation for players on strategies to avoid injurycompleted PRIOR TO and DURING sport seasonAt least 2-3 times per week x 15 min each sessionMost important factor – strengthening, pre-season training and between seasons continue strengthening for sport specific activities.Each sport can be broken down into basic fundamental movements. The art of designing a prevention program is identifying movement patterns unique for a given sport.
10Jumping Technique Land: on the balls of the feet knees flexed (initially ~ 20 deg and then bend to about 40 deg) - Simple cue to land “softly” has been shown to decrease force at the ACL 3chest over the kneesavoid excessive movement of the knee upon landing (inward or forward) – keep knee over the middle of the footKeep hips straight – don’t turn out hipsEqual weight on the right and leftExcessive motion of the knee in an inward motion is valgus – this may be used during demonstration of exercises.Form during squatting exercises should be similar – avoiding excessive motion of the knee, keeping knee over middle of the foot, keeping hips straight, equal weight.
11Jumping TechniqueJumping technique – watch for knees coming together during the first jump
12Basketball injury Rebecca Lobo basketball injury Watch during landing on the left foot – knee falls inward
13Knee alignmentNote on the good side – knees over the middle toe region (not fallen inward) , equal weight on both sides
14Why land with knee bent?Quad muscles works to extend the knee region – also pulls the lower leg bone forward (tibia) relative to the upper leg bone (femur)ACL prevents this forward movement of the tibiaHamstring muscles work to bend the knee and pull the tibia backward (works with the ACL)Hamstring allows the muscles to absorb the force when landing and supports the ACLLanding with knee bend causes less stress at the ACL and allow muscles to absorb the forceFemurfemur
15Strengthening Component Balance between the hamstring and quad musclesrecommended that the hamstrings be % as strong as the quadsWork on the hip muscles to stabilize knee and control knee
16PlyometricsDesigned to produce fast, powerful movements, and improve the functions of the nervous systemExamples: squat jumps, drop jumps, boundingHas been shown to be one of the most effective tools to reduce non-contact ACL injuries 4
17Agility Cutting, changing directions, changing speed of movement Tips for safe agility training:Keep body moving in direction you are goingKeep center of mass over your feetDon’t overcutCareful of knee position
18What does research sayLim et al. “injury prevention program could potentially modify the flexibility, strength and biomechanical properties associated with ACL injury and lower the athletes risk for injury”Female basketball student who had injury prevention 20 min warm up every practice demo increased strength and flexibilityGilchrist et al. studied just under 1500 collegiate athletes:70% reduction in ACL injury with noncontact injury40% overall reduction in ACL injuryGilchrist: randomized control trial: intervention and control group – neuromuscular training 3 x per week
19ReferencesDubljanin-Raspopovic E, Bumbasirevic M, Devecerski G, Matanovic D. The effects of functional knee bracing after anterior cruciate ligament reconstruction. Med Pregl Sep-Oct;62(9-10):483-7.Bien DP. Rationale and implementation of anterior cruciate ligament injury prevention warm-up programs in female athletes. J Strength Cond Res Jan;25(1):Laughlin WA, Weinhand JT, Kernozek TW, Cobb SC, Keenan KG, O’Connor KM. The effects of single-leg landing technique on ACL loading. J Biomech. 2011Jul7:44(10): Epub 2011 May 10Lim BO, Lee YS, Kim JG, An KO, Yoo J, Kwon YH. Effects of sports injury prevention training on the biomechanical risk factors of anterior cruciate ligament injury in high school female basketball players. Am J Sports Med Sep;37(9): Epub 2009 JunGilchrist J, Mandelbaum BR, Melancon H, Ryan GW, Silvers HJ, Griffin LY, Watanabe DS, Dick RW, Dvorak J. A randomized controlled trial to prevent noncontact anterior cruciate ligament injury in female collegiate soccer players. Am J Sports Med Aug;36(8):Willy RW, Davis IS. The Effect of a Hip Strengthening Program on Mechanics During Running and During a Single Leg Squat J Orthop Sports Phys Ther Jul 12. [Epub ahead of print]Lubahn AJ, Kernozek TW, Tyson TL, Merkitch KW, Reutemann P. Chestnut JM.Hip muscle activation and knee frontal plane motion during weight bearing therapeutic exercises. Int J Sports Phys Ther Jun;6(2):R Tyler Hamilton, MS, ATC, Sandra J Shultz, PhD, ATC, CSCS, Randy J Schmitz, PhD, ATC, and David H Perrin, PhD, ATC, FACSM. Triple-Hop Distance as a Valid Predictor of Lower Limb Strength and Power. J Athl Train Mar-Apr; 43(2): 144–151.