ACL Facts Athletes Need to Know

Learn about one of the athlete's most important ligaments through this article about ACL facts from STACK expert Joe Giandonato.

The possibility of a knee injury looms ominously throughout an athlete's career. The most dreaded, the ACL tear, is known for robbing players of their speed and explosiveness. Combine that with the laborious rehabilitation process, and it's easy to understand why reclaiming confidence following an ACL injury is difficult even for the most dedicated competitors. (Check out STACK's Athlete's Guide to the ACL.)

The anterior cruciate ligament, better known as the ACL, attaches to the tibia and blends into the meniscus. Its purpose is to help stabilize the knee in near- and end-range extension. In conjunction with the posterior cruciate ligament, the medial and lateral collateral ligaments and the hamstring muscles, it also helps prevent anterior, posterior and rotational movement of the tibia to resist inward collapse, outward angulation and lateral rotation of the knee. To say the ACL is important for athlete performance is a huge understatement.

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ACL Examination

The possibility of a knee injury looms ominously throughout an athlete's career. The most dreaded, the ACL tear, is known for robbing players of their speed and explosiveness. Combine that with the laborious rehabilitation process, and it's easy to understand why reclaiming confidence following an ACL injury is difficult even for the most dedicated competitors. (Check out STACK's Athlete's Guide to the ACL.)

Functions of the ACL 

The anterior cruciate ligament, better known as the ACL, attaches to the tibia and blends into the meniscus. Its purpose is to help stabilize the knee in near- and end-range extension. In conjunction with the posterior cruciate ligament, the medial and lateral collateral ligaments and the hamstring muscles, it also helps prevent anterior, posterior and rotational movement of the tibia to resist inward collapse, outward angulation and lateral rotation of the knee. To say the ACL is important for athlete performance is a huge understatement.

Causes of Injuries

Around 80 percent of knee injuries result from non-contact movements, ranging from hyperextension to buckling inward or rotating forcefully during slight knee flexion. Many of these injuries can be attributed to poor control of the trunk, or to weakness in the core musculature and posterior chain. (This region includes the gluteals and hamstrings, which work together to reduce knee movement during activity.)

Females at Greater Risk

Female athletes who engage in sports that involve jumping and pivoting are at far greater risk of sustaining an ACL injury. There are various reasons for this, but typically it's because females have stronger quadricep muscles in relation to their posterior chain muscles, coupled with weaker and more moveable core muscles. Although men and women have somewhat different neuromuscular profiles, proper training can address weaknesses and reduce the likelihood of sustaining a knee injury.

Preventing Knee Injuries

Core Training

Training the core is a priority, especially since research suggests that uncontrolled trunk and hip movements when cutting and landing can prompt knee abduction motion and hip adductor torque when an athlete attempts to stabilize and balance in landing. Ideally, the core should be trained to resist movement. Use variations of Bridge and Plank exercises, because they fortify trunk stability.

Posterior Chain Training

Training the posterior chain is another major point of emphasis. Start with light load exercises around the hip hinge, like One-Legged Deadlifts, Romanian Deadlifts and Overhead Squats. Exercises using TRX straps can also be incorporated to engage the quadriceps and posterior chain simultaneously.

Absorbing Force

Low-level plyometric exercises are an integral part of injury prevention. Plyos challenge core stability as well as the posterior chain muscles during landing and jumping movements. These movements can be progressed as athletes advance. They are typically used for transitioning from late stage rehabilitation to the court or field.

Prevention Exercises

Glute Bridge with Band Abduction

Sets/Reps: 2x20-30 seconds or 2x10-15 reps

  • Lying on back, place elastic band around both thighs, slightly above knee
  • Bend knees and plant heels directly under knees, keeping them hip-width apart
  • Brace core and drive heels in ground to extend hips
  • Focus on driving knees outward, keeping legs spread against pull of band
  • Keep hips as high as you can, driving them toward ceiling
  • Hold for specified time
  • Return to starting position and repeat for specified reps

Banded Side Plank Row

Sets/Reps: 2×10-15 each side

  • Attach elastic band to column or rack, secure it with anchor, or tying it in a knot
  • Assume side lying position, with body in one straight line, keeping arm beneath you
  • Using forearm beneath body, lift hips toward ceiling
  • Keep shoulders and hips square and side of bottom foot firmly planted on ground
  • Grasp end of elastic band with hand of free arm
  • Keeping shoulders and hips square, row the band, driving elbow of top arm toward midline of body
  • Repeat for specified reps

One-Legged Dumbbell Romanian Deadlift

Sets/Reps: 2×10-15 each side

  • Firmly grasp relatively light dumbbell in each hand
  •  Space feet slightly narrower than hip-width
  • Keep slight bend in both knees
  • Keep chest tall by pulling shoulders down and back
  • Tuck chin and brace core
  • Drive heel of right foot into ground
  • Pick left leg up off ground, straighten knee, and bring heel in line with hips
  • Keeping shoulders back and chest out, move torso forward, away from hips, maintaining firm grip on dumbbells. Dumbbells should stay in near contact with body and should not descend below knee
  • Return to starting position by extending hips
  • Squeeze glutes at top of movement
  • Repeat movement for specified reps then switch sides

TRX Squat 

Sets/Reps: 2×10-15

  • Grip handles of TRX suspension system mounted on wall or securely looped around pull-up bar or power rack
  • Grasp handles firmly, keeping feet firmly planted hip-width apart
  • Tighten core and drive hips rearward, pulling body away from straps
  • Lower hips no further than knee height, ensuring that spine remains neutral
  • Drive hips up during ascent, driving heels through ground
  • Squeeze glutes at top to complete hip extension
  • Repeat for specified reps

 Drop Landings from 12-inch Box

Sets/Reps: 2×5-10

  • Stand on low plyometric box, step, or stackable aerobics platform
  • Hop off elevated surface
  • Land on balls of feet and quickly roll back onto heels by shooting hips back
  • Land with core tight and shoulders directly in line with knees
  • Stick the landing for two full seconds before next rep
  • Repeat for specified reps


Photo Credit: Getty Images // Thinkstock

Topics: ACL INJURY | INJURY | HEELS