Anterior cruciate ligament (ACL) injuries are common in sports involving landing from a jump, sudden deceleration, cutting and pivoting. The majority of ACL injuries are noncontact injuries (3, 8, 18). Research has shown that female athletes are 4 to 6 times greater risk of injuring their ACL than male athletes playing similar sports (1, 2, 15).
How to help prevent knee/ACL injuries? In short…
The 2 biggest problems linked to ACL injuries:
1. Posterior chain deficiencies – weak hamstrings, glutes and spinal erectors
2. Poor deceleration mechanics – jumping and turning
5 Factors to Help Prevent ACL Injuries:
1. Lower limb alignment – proper lifting mechanics (athletic position)
2. Muscular strength – posterior chain and stabilizer strength
3. Neuromuscular activation – faster hamstring reaction time, proper deceleration/jumping and turning mechanics (jump stop, toe landings)
4. Training/conditioning level – muscular endurance, muscle memory/proprioception
5. Dynamic Warm-up
Recent article in the NY Times about ACL injuries in female basketball players: http://www.nytimes.com/2011/03/27/sports/ncaabasketball/27acl.html?_r=1&emc=eta1
In More detail, what research shows us is there are several intrinsic and extrinsic factors have been suggested to be contributing to the increased risk of ACL injuries in female athletes (2, 8, 12).
Causes – two categories:
1. Intrinsic Factors:
a. Muscle strength – weaker hamstrings in relation to the athlete’s quadriceps
b. Neuromuscular activation / control
2. Extrinsic Factors:
a. Sport activity
b. Training / conditioning level
From of the above factors, the most important factor is neuromuscular control (8). Neuromuscular control within the knee is the unconscious activation of muscles crossing the knee joint in response to sensory stimuli. During athletic movements, the kinematics (body’s motion without consideration of the forces that cause the motion) and kinetics (causes of motion) are what lead the athletes to an ACL injury (4, 5).
Typical Injury Scenario(s): Most commonly when the athlete suddenly stops and turns resulting in a sudden deceleration for the lower limb in addition with a forceful hyperextension (straightening) of the knee or femoral rotation. Also, occurs when an athlete lands in an extended knee position or “toe lands” position when jumping. These positions are extremely unstable and when tied with a forceful quadriceps contraction, can be significant contributors to ACL injuries.
When athletes perform athletic movements such as landing from a jump, cutting and decelerating, there is a large interaction within the knee joint to maintain functional joint stability between ligaments, soft tissues and bone-on-bone forces (4, 13).
3 Neuromuscular Control Imbalances common in female athletes and place the athlete at an increased risk of serious knee injury:
1. Ligament Dominance
a. Valgus Movement or knock-knee position - When ground reaction forces (GRF) within athletic movements are absorbed by knee ligaments (9). Most commonly occurs in running and cutting movements (14, 16), landing from a vertical jump (5, 6, 7, 10) and landing from a backward jump (5).
2. Quadriceps Dominance
a. Female athletes tend to generate less hamstring force relative to body size, more quadriceps force and activate their quadriceps before their hamstrings in comparison to men.
b. When the tibia tends to shift forward, which can result in an ACL injury, female athletes tend to activate their quadriceps to stabilize the knee, whereas male athletes tend to utilize their hamstrings (11). The hamstrings have a line of pull that can pull the tibia backwards, decreasing the stress on the ACL (17).
3. Core Stability
a. The muscles that maintain proper alignment of the lumbo pelvic-hip complex are hip external rotators, gluteal muscles, hamstrings, abdominal muscles, quadratus lumborum, erector spinae and multifidus. Weak core muscles are a contributing factor to increased valgus movement at the knee with repetitive jumping (19).
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Hello, my name is Stacy Phillips, licensed Functional Nutritionist and Holistic Health, Wellness and Strength & Conditioning Coach with a MS in Human Nutrition and Functional Medicine practicing whole-foods nutrition and physical training to individuals around the globe.
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