Injuries to the anterior cruciate ligament (ACL) are increasingly common. Every year, approximately 80, 000 people rupture their ACL in the United States alone. Of those, it is mostly the young and active population that suffers the injury. This book provides an overview of the psychological models of injury rehabilitation, the role of coping with ACL injury and the role of social support. Detailed discussions are included related to specific stages of rehabilitation from ACL injury. Furthermore, to investigate the subtle biomechanical changes in the knee following ACL deficiency and reconstruction, both in vitro robotic testing systems and in vivo imaging and computerized modeling techniques have been employed and are examined.