With an increasing population of athletes, there are correspondently an increased number of anterior cruciate ligament injuries. It is now estimated that 100,000 athletes will have this injury during the next year. For many, this will result in surgery and an extensive rehabilitation program for six to twenty-four months. Unfortunately only 75% of those individuals return to their previous activity level.
The incidence of anterior cruciate ligament injuries is three to four times greater in the female athlete when compared to the male athlete in the same competing sport. Approximately 70% of anterior cruciate ligament injuries are noncontact and usually occur as the athlete undergoes rapid deacceleration while performing either a planting and cutting maneuver or landing from a jump. The young female athlete is especially at risk.
The risk factors identified are anatomic, hormonal, environmental and biomechanical. Biomechanical factors appear to be the most important contributors to the greater risk of anterior cruciate ligament injuries in the female athlete. Some fundamental differences in body mechanics of woman when compared to men are primarily at fault. First, women have a straighter or less flexed knee when performing certain maneuvers in running, cutting and jumping. This results in a straighter hip and ankle and to compensate the hips are externally rotated and the knees deviated slightly more outward. These factors place more strain on the anterior cruciate ligament.
There is a significant difference between quadriceps and hamstring strength in male and female athletes. When adjusted for body weight, the female athletes hamstrings are weaker. The female athlete also activates their hamstring tendons less than their quadriceps tendons when landing. Finally the female muscle stabilization, i.e. activating the quadriceps and the hamstring muscles to stabilize the knee, takes a millisecond longer to respond than their male counterpart. With wider hips, there are increased angular forces involving the female athletes knee which may increase torque or rotational twist on the knee which again will stress the anterior cruciate ligament.
Anatomic cross-sectional size or area of the anterior cruciate ligament in the female athlete is less than that of the male athlete. The space in which the anterior cruciate ligament travels is smaller than that in a male athlete. The combination of both factors may also contribute to increased anterior cruciate ligament tears in the female athlete.
The womans muscle tissue is more flexible than the males muscle tissue. This flexibility is another important cause or relationship for increased anterior cruciate ligament tension and tear. Normal changes in the female athletes menstrual cycle may at times lead to both more muscle and ligamentous tissue elasticity which would also potentiate anterior cruciate ligament tears in the female athlete.
Based on our research and knowledge, prevention programs to reduce stress on the anterior cruciate ligament and thereby reduce anterior cruciate ligament tears in the female athlete are now being developed.
A University of Vermont Medical Schools study noted a 69% decrease in injuries among the female ski patrol personnel. In Cincinnati, a six-week program of training reduced female anterior cruciate ligament injuries to equal that of the male athlete.
These programs are now being offered by physical therapists and athletic trainers who specialize in sports related injuries. Female athletes will be trained to alter their strength, muscle recruitment and movement patterns. Anterior cruciate ligament stress will be reduced by increasing quadriceps and hamstring strength, increasing hamstring activation time, increasing knee flexion when deacceleration, landing and cutting to equal the male athlete, and keeping the knee straight during this increased flexion thereby reducing external tibial rotation or deviating the knee joint outwards.
The training program will incorporate balance training to improve position awareness, proprioception and balance. This will improve the bodys sense of potential injurious movements and facilitate a protective response to increase synchronous muscle contraction involving the knee joint to improve joint stability. Plyometric agility training is also part of the physical training program. This incorporates jumping, bounding, leaping as well as rapid change of direction exercises. This program is noted to improve hamstring muscle strength, reduce ground impact reaction forces, and improve flexibility and voluntary muscle response times to control the rotation and translation. There is now evidence that training programs that incorporate balance and plyometric agility exercises are able to reduce the risk of anterior cruciate ligament injuries in the female athlete. It is therefore recommended that these programs be incorporated into the female athletes training program both before and during the sports season.