A healthy and functional anterior cruciate ligament (ACL) is a requirement for run, jump, and pivot sports. The complete rupture most often requires major surgery and rehabilitation.
Although the surgical techniques have dramatically improved, there remains the potential for a career ending or diminished performance outcome and increase incidence of knee arthritis from an ACL injury. It is well documented in a variety of sports that female athletes injure their ACL up to ten times more frequently than male athletes.
The incidence varies depending upon the sport with the highest risk sports including basketball, soccer, and volleyball. However, a large majority of ACL injuries occur in non-contact movements. The reason for the increased frequency of ACL injuries in females is not known, yet a variety of potential causes or factors have been postulated. Some of the differences between males and females that may contribute include anatomical, hormonal, and muscular/neuromuscular. Anatomical Differences in Females
The ACL resides in the intercondylar notch. The female “notch” may be narrower and/or shallower allowing a guillotine mechanism to occur.
- Alignment. Females may have excessive loads on the ACL due to being knock-kneed (genu valgum), hips rotating internally, and/or external tibial torsion.
- Females have increased joint laxity allowing the joint to move beyond the “breaking point.”
- Females have a smaller ACL that is unable to resist the forces on the joint. Hormonal Differences in Females An accepted rule of nature known as Wolf’s law would predict that an ACL would increase in strength with exercise.
However, research using tissue cultures has demonstrated the following:
- Increasing estrogen concentration in tissue culture decreases ACL strength due to decreased collagen synthesis.
- Increasing estrogen concentration in tissue culture has shown a decreased load to failure in rats.
- There are specific highly specialized enzymes in both males and females. However, in females these enzymes appear to be counter productive and do not protect the ACL.
Collectively, these factors decrease the ability of the female ACL to become stronger. Muscular/Neuromuscular Differences in Females In females, decreased muscular strength, complex and intricate relationship of the nervous system and muscle interactions, and decreased response times provide the knee joint with a subtle but unfortunate lack of ability to respond quickly enough to prevent abnormal joint motion and excessive loads on the ACL.
Females have a lower co-contraction potential placing more stress on the ACL. The ACL must resist the anterior translation of the tibia to prevent ACL injury. This requires maximal co-contraction of the quadriceps and hamstrings with running, deceleration, jumping, and pivoting activities. Furthermore, it has been shown in female athletes that the strength ratio of the hamstring vs. quadriceps is 40% compared to 60% in male athletes.
These imbalances contribute to the delicate and dynamic forces placed on the ACL and susceptibility to injury.
PREVENTION Based upon these theories and as research continues, there exists preventive treatment measures. Some physicians advocate control of the menstrual cycle. Others focus on agility, plyometric, and jumping drills, which have shown success in an effort to counter the anatomic and muscular factors. SportExcel Health and Human Performance recommends specific protocols that can be incorporated into all athletes’ training programs both male and female to increase joint and ACL stability.
Below are some examples of stretching and strength and balance exercises.
Hamstring stretching should be done in multiple planes of motion in conjunction with an active warm-up. Trunk and arms should be stretched in addition to all parts of the legs. The stretch in this photo can be modified by changing the position and orientation of the front foot.
This particular stretch of the quadriceps emphasizes balance. The knee should remain below or behind the hip during the stretch. Quadriceps stretching should also be done in multiple planes of motion in conjunction with an active warm-up. Other quadriceps stretches emphasize different parts of the muscles.
Single leg balance with head turning improves balance and agility. The head motion should be changed in terms of tempo and direction to maintain a challenge. Other motions can be added to single leg balance. Closing one or both eyes or blinking increases the challenge.
Balance and abdominal strength are an integral part of an ACL program. This exercise emphasizes both. As the trunk moves backward relative to the standing leg, the abdominals, quadriceps and hip flexors work to maintain balance.
This is an example of an abdominal strengthening exercise. The abdominal muscles help control the pelvis and trunk and, therefore, are an essential part to a healthy knee.
Lunges are a good strengthening exercise. This photo shows a lunge with a head turn, again emphasizing balance and coordination. Lunges should be done in multiple planes of motion. Contrast this motion to the one in the previous photo.
Jumping is a good drill for strength, agility and coordination training. Optimal landing technique includes landing with flexed knees and hips (approximately 30 degrees) and the trunk forward to the hips.
Provided by
