An ACL injury is a common experience that can be avoided through awareness. ACL tears are non-contact injuries that are related to a deficit in eccentric control during cutting, running, or jumping. As a result, these activities produce high-intensity loading to the tissues of the knee. This can cause the ligaments to fail if your muscles are not strong enough to control these forces. Strength, stability, balance, and coordination decrease the risk of non-contact ACL injuries. These are trainable qualities that help improve eccentric control and single limb stability. At Symmetry we can treat a variety of injuries virtually, including ACL injury.
Examples of neuromuscular control deficits may include decreased muscle strength, power, or poor activation patterns. Deficits in these areas will place increased loads on the ACL during competition. Patients/athletes will utilize compensatory movement patterns to hide their deficiencies, placing them at increased risk of injury. These patterns are typically adopted to keep themselves on the field for as long as possible. But, eventually these movement faults cause failure of tissue.
First, Ligament dominant patterns present as decreased dynamic knee joint stability with an inability to control the knee in the frontal plane of motion while cutting or landing. We typically see this as dynamic knee valgus.
Quadriceps dominance is an imbalance between quadriceps/hamstring strength, recruitment, or coordination causing a more stiff landing pattern.
Leg dominance is an imbalance between one leg and the other. Leg-dominant athletes prefer to use one leg more than the other to compensate for weakness or pain.
Trunk dominant movement patterns rely on the trunk to act as a counterweight to dissipate force rather than the muscles of their LE.
A thorough movement assessment is required to identify these deficits. It’s great see my athletes perform DL squat, SL squat, DL jump, SL hop to get an idea of how well they are as movers. Higher level movement patterns such as SL hop testing, agility, and running assessments are added as appropriate. The tuck jump is used as a screening technique to identify those individuals who may be in greater risk of a non-contact ACL injury.
Tuck Jump Assessment
The tuck jump is a repetitive jumping test that has the patient jump in place while bringing their knees up as high as possible. The goal is to have the patient land in the same footprint and continuously jump for 10 seconds. The test may be discontinued if the patient demonstrates a sharp decline in form before 10 seconds. The scorer is looking to assess knee and thigh motion, foot position during landing, and plyometric technique.
- Knee and thigh motion
- Lower extremity valgus
- Thighs do not reach parallel (peak of jump)
- Thighs not equal side to side (during flight)
- Foot position during landing
- placement not shoulder width apart
- not parallel (front to back)
- contact timing not equal
- excessive landing contact noise
- Plyometric Technique
- Pause between jumps
- Technique declines prior to 10 sec
- Does not land in same footprint (excessive in-flight motion)
Modifiable ACL Injury Risk Factors
The scoring of the tuck jump will lead to identify which neuromuscular deficits are present that place the athlete at a higher risk of injury. This is a crucial screening tool to be able to identify high risk athletes. In addition, it is used to select the correct intervention to optimize your exercise programming.
Ligament dominant patients demonstrate dynamic knee valgus or foot placement that does not remain shoulder width apart.
Quadriceps dominance – excessive landing contact noise, stiff knees, and poor shock absorption.
Leg dominance – when the thighs are not equal (side to side) during flight, improper foot contact timing, or foot landing is not parallel (front to back).
Trunk dominance – when the thighs are not reaching parallel at peak of flight.
Pausing between jumps is evidence of poor coordination, eccentric control, and power.
ACL Injury: Males vs. Females
Females are more susceptible to non-contact ACL injuries compared to males. The anatomical or hormonal differences are the primary cause that increases the risk of ACL injury amongst the female population. However, static anatomical measures do not appear to correlate with increased injury risk. Hormonal changes still remain unclear as to how much they contribute to injury risk. Although, the differences in force production, strength, and neuromuscular activation patterns that contribute to the increased injury risk in females. Neuromuscular control deficits appear to be predictive of ACL injury in athletes that present with high-risk landing techniques.
Women demonstrate decreased hamstring activation with increased quadriceps dominant patterns during landing causing stiffer landings. They also have greater side-to-side differences in peak hamstring torque causing increased leg and quadriceps dominance. Women demonstrate increased dynamic knee valgus angles causing increased reliance on their ligaments for stability. Lastly, they demonstrate increased hip adduction angle during single-limb landing causing increased dynamic knee valgus. Men tend to demonstrate greater power, strength, and coordination through puberty, which better prepares them to handle the forces of deceleration during cutting, running, and jumping.
Impact on Rehab and Training
These findings are helpful to be able to determine high-risk landing mechanics and provide them with proper exercise prescription to make adjustments to their landing techniques. The good news is all of these neuromuscular deficits are trainable.
We can improve movement efficiency with proper exercise selection and provide specific exercises to improve strength, power, stability, shock absorption, and eccentric control. These are all modifiable objective deficits that will translate to improved performance and decreased risk of injury with proper exercise prescription. Ready to get started on physical therapy? Book a session with us in clinic or virtually!
Written By: Dr. Timothy Alemi, PT, DPT, SCS
- Myer GD, Brent JL, Ford KR, Hewett TE. Real-time assessment and neuromuscular training feedback techniques to prevent ACL injury in female athletes. Strength Cond J. 2011;33(3):21-35.