Kinesiology

Topics: Knee, Anterior cruciate ligament, Extension Pages: 11 (3121 words) Published: June 22, 2013
Danielle Wagner
Kinesiology Biomechanics Project Outline

Analyzing Motion:  A Knee during Jumping/Cutting of a Female Soccer Player Intro:
The anterior cruciate ligament (ACL) is one of the most common, severe, and devastating knee injuries in men and women in both contact and non-contact sports. Within the past 20-303 years the prevalence of ACL tears has been noted more significantly in the female athlete. Females were two times as likely to have ACL injuries as a result of player contact and three times more likely to obtain such an injury through noncontact mechanisms as their male counterparts1. The latest research2 indicates that female athletes are two to eight times more likely to experience anterior cruciate ligament rupture than male athletes. Mechanics of a woman’s body are leading to more ACL injuries. Numerous theories have been suggested to explain this problem. Many of these theories4,5 include both extrinsic and intrinsic factors. Intrinsic factors would be considered uncontrollable, and would include greater physiological rotatory laxity, smaller size of ACL associated with smaller intercondylar notch, valgus malalignment, hyperextension, diminished proproception, leg dominance, quadriceps dominance, hormonal influence, and postural alignment. Extrinsic factors would be considered potentially controllable. These include decreased strength and conditioning, inappropriate shoes, motivation, deceleration forces during injury, neuromuscular control, and body movement8. These extrinsic factors are the focus of prevention of ACL tears in the female athlete. Due to these factors, many questions have arisen regarding the increasing rate of ACL tears in the female athlete. ACL background:

The ACL is made of two bundles, the anteromedial and posterolateral. Both of these bundles originate from the posterior medial femoral condyle and insert into the anterior medial aspect of the tibial plateau6. In addition to the ligament itself, other soft tissues provide secondary support to the knee. These secondary support structures7 are the tendons and muscles, namely the quadriceps, hamstrings, and the gastrocnemius. Both the hamstrings and gastrocnemius are important in that they provide a posterior force on the tibia that helps to counteract anterior translation. The ACL is the primary restraint to anterior tibial translation, and it also provides secondary restraint to internal rotation, as well as varus/valgus angulation with the knee in full extension13. The quadriceps and hamstring muscles further stabilize the joint. It’s known that ACL injuries occur in a variety of ways. Non-contact mechanisms must involve anterior sheer of the tibia in relation to the femur. The quadriceps can produce significant anteriorly directed forces on the tibia, especially in the area of 0 to 40 degrees of knee flexion. The magnitude of the quadriceps’ force can be influenced by the muscle size, the degree of central nervous system activation, and the velocity of movement12. In addition, eccentrically loaded muscle can develop much more force than muscle that is shortening. These factors can theoretically produce enough force to tear the ACL.

Female athletes at the high school and collegiate level in the United States suffer more than 30,000 serious knee injuries each year16. In recreational sports, the number of injuries is even greater. Many of these injuries are anterior cruciate ligament (ACL) tears. Why women are 2 to 8 times more likely than men to sustain ACL tears, especially in sports like soccer that involve deceleration, twisting, cutting, and jumping, continues to be a challenging question. Differences in the anatomy, knee alignment, hormonal profile, muscle strength, and conditioning of men and women are just some of the possible reasons for the different rates of injury13. Some factors include:

* Anatomic Differences
* Alignment of the knee
* Hormonal factors
* Muscle and strength conditioning...
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