ACL (Knee) Injury Prevention

Problem: Non-contact ACL injuries (2x to 10x in females) = biomechanics, equipment, and training 

Solution: ACL injury prevention interventions to correct technique/movement pattens

Non-Trainable Risks: Anatomy cannot change; thus, techniques must be coached to alleviate as much stress on the ACL as possible. Athletes facing these challenges may have to put in extra work.

·  Valgus Stress From “Q-Angleâ€: Larger Q-angle stresses on the ACL.

·  Intercondylar Notch of the Femur: The ACL passes through this bony structure. A narrow intercondylar notch creates more friction on the ACL

·  Hormone Differences Between Males & Females: eg relaxin  

Trainable Risks: Balancing strength around joints and correcting flawed movement/motor programs can reduce the incidence of non-contact ACL injuries

·  Quadriceps Dominance: Shin bone gets pulled forward thus shearing the ACL

·  Valgus Stress from Technique or Muscle Imbalance/Inhibition: Knee caves inward

·  Lack of Control Over Centre of Mass: Poor weight distribution over the base of support contributes to flawed lower body mechanics. Eg: valgus stress on knee

                                 Common Incidents Leading to Injury:

·  One step stops: COG over base of support leading to valgus stress on knee

§  Train: Trunk control/core (sagittal plane)

§  Coach: Short choppy steps before stops

§  Drill: One step stops expected and unexpected at appropriate intensities

·  Cutting tasks: Lack control of tibial rotation

§  Train: Hip Airplane (horizontal plane)

§  Coach: Hip Alignment and weight distribution over base of support

§  Drill: Agility ladder

·  Sudden changes of direction: COG over base of support 

§  Train: Core strength, endurance, and timing (frontal plane)

§  Coach: Deceleration using principle of impulse (change in momentum = force x time) 

§  Drill: arm swing and ROM at hips, knee, & ankle 

·  Lapse in concentration: New motor programs become the default (unconscious competence) 

§  Train: Groove essential motor programs

§  Coach: Reps at appropriate intensity

§  Drill: Dual tasking 

·  Rotation at the knee (tibia): Learn to recognize & avoid high risk situations, 

·  Landing from a jump with inadequate knee and hip flexion

o  Assess squat, posture, ROM, muscle imbalances, remove faulty motor patterns and replace with improved  (Kinesiopathologic model exam) 

o  Train: based on specific person-to-person findings in KPM exam 

o  General Training and Coaching Strategies 

§  Ensuring movement occurs through sagittal plane

§  Practice “soft landing†= absorb landing force over greater ROM, initial landing on forefoot, knees track over toes 

§  Training: reduce quad dominance by training hip extensors and knee flexors. 10 weeks of ACL injury-prevention training decreased knee extensor moments and increased hip extensor moments 

§  Motor learning: experience dependent plasticity refers to alterations in the brain in response to motor-skill learning. Skill acquisition training is superior at reduce ACL injuries compared to strength training ***consider quad dominance!

§  Core training: trunk control, body awareness, and decision making = control over COG relative to base of support

§  Coaching: practice game situations ie players practice unanticipated changes in direction ***ensure appropriate intensity based on athletes’ capabilities

·  Consider: continuum of open – closed systems