Injury to the anterior cruciate ligament (ACL) is something that sparks the attention of the general public. Derrick Rose’s ACL tear practically turned the entire city of Chicago upside down and more recently he suffered another knee injury that had the entire sports nation holding its’ breath. It goes without saying that the general population is well aware of the impact that a ruptured ACL can have on a player’s life. In recent years more and more research has been done to investigate how these injuries may be prevented.
Neuromuscular training programs such as Sports metrics and Prevention Injury and Enhance Performance (PEP) are at the forefront of preventative care for injuries to the knee. This blog will first discuss other factors that may predispose yourself to injury and also discuss the components of these neuromuscular training programs.
The incidence of non-contact ACL injury has increased since the introduction of Title IX in 1972 which brought about more equality for women in many realms, including athletics. As single sport specialization continues to be more and more prevalent in young athletes (read our blog from 10/12/12 entitled Too Much, Too Soon to learn more about this phenomenon), the incidence rate of these soft tissue injuries is also becoming more prevalent.
Most commonly ACL injuries during sport participation results from a moment of deceleration and pivoting. Sports maneuvers such as this may lead to high external knee loads in both sexes. Why has this caused more issues in the female population? Up until recently this was unclear and it still needs further examination. It is believed that three major etiological factors may cause the gender disparity observed in ACL injury rates: anatomic, hormonal and neuromuscular.
There have been countless studies that have focused on anatomical measures such as intercondylar notch width and Q-angle, the Q-angle being the measurement of the angle made up by the anterior superior iliac spine, the middle of the patella (kneecap), and tibial tuberosity (see figure 1).
Hormonal factors, particularly those associated with the follicular and ovulatory phases of the menstrual cycle have also been linked to ACL injury risk. The way and amount that female hormones affect ACL injury is still not fully understand.
So that leaves neuromuscular factors which brings us back to the topic of injury prevention. Unlike anatomical and hormonal factors, we as clinicians believe that there are actions that we can take to correct the neuromuscular factors that may lead to more ACL injuries in women. There is four primary sub-sections to the neuromuscular factor in women; ligament dominance, trunk dominance, limb dominance, and quadriceps dominance.
Ligament dominance refers to the fact that muscles do not sufficiently absorb the ground reaction forces (GRF), so the joint and the ligaments must absorb high amounts of force over a brief time period. As mentioned before, females typically have a wider Q-angle. Due to this, females often place their center of gravity to the side more so than men which places more stress on the ligament. Assisting in this matter is the fact that females often display a limited amount of trunk stability. In the heat of athletic participation, the female athlete is less suited for maintaining their center of gravity in a neutral position. It has also been shown that women, for the most part, are more one side dominant. When a female tears her ACL, in many instances the majority of her weight in on the affected side.
A major neuromuscular dysfunction that is often seen in the female population is the early activation of the quadriceps group to stabilize the knee, whereas men primarily utilize the hamstring group. The quadriceps make their way down the front of the thigh and knee then attach to the tibia. When the quads are primarily used to stabilize the knee, an anterior (forward) shearing force is placed on the tibia further placing stress on the ACL.
A primary focus in many studies in this area is jump-landing mechanic training to correct these issues. Often female athletes lack the ability to properly land. An ideal landing mechanic involves the knees facing straight forward, knees behind the toes, knees bent, hip flexed, butt back, forward facing chest, and a subtle landing on the balls of the feet. Unfortunately what often causes increased stress to the ACL in women is a valgus moment at the knees (knock-kneed) and a static stance (limited knee and hip flexion).
Two major neuromuscular training programs exist in current literature; Prevention Injury and Enhance Performance and Sports metrics. In a recent study performed by Noyes et al, 42 ACL injury prevention programs were evaluated resulting in a consensus that the PEP and Sports metrics were most optimal in decreasing the likelihood of ACL injury and increasing sports performance.
The focus of these programs is to correct the four areas of neuromuscular control listed above through the use of dynamic warm up, plyometrics, strength training, flexibility, and agility exercises. Different programs are implemented for varying amounts of time most often falling between six weeks to three months. Although this is the time frame that the studies use, neuromuscular training must be maintained to resist the urge to fall back into poor patterns.
Over the course of these programs, a trained individual must be present to ensure proper mechanics. The patient must constantly be encouraged to use proper technique. If the patient undergoes the program without proper instruction then poor mechanics can be reinforced leading to the possibility of increasing the risk of injury.
Although the implementation of a neuromuscular training program is encouraged, it in no way will definitively stop injury from happening. As with any other activity, injury may occur during the training program. Please consult a physician before enrolling in a neuromuscular training program.
Below are links describing neuromuscular training programs and another very well done article about the increase in ACL injuries.