The book presents an overview of available Computer Assisted Orthopaedic Surgery (CAOS) solutions to assist with adult reconstructive hip and knee procedures. The benefits of CAOS in clinical practice include improved planning, increased accuracy, intraoperative information and guidance, andthe potential to enable less or minimally invasive surgery without loss of accuracy. The book reflects the current state of the art in computer integrated surgery, with the emphasis on clinically tested systems and procedures. The application of technologies such as surgical navigation and robotic surgery, medical imaging, surgical planning and simulation in total or partial hipand knee reconstruction procedures is presented. The range of currently employed approaches is covered, spanning from active robotics to navigation based medical images - either preoperative or inreoperative, and image-free navigation. The first part of the book offers the clinical rationale for the use of CAOS procedures, and describes the basic technological building blocks of such procedures and systems. The second part of the book describes specific applications in total hip replacement, total and unicompartmental kneereplacement, osteotomies around the hip and knee, knee ligament reconstruction and hip and knee trauma. The clinical goal, the technological approach, and the clinical results are outlined for every application. The book is intended for practising orthopaedic surgeons, fellows, residents-in-training and medical students interested in the latest technological developments in computer assisted surgery, as well as for engineers and developers interested in learning more about the interaction of advancedtechnology with orthopaedic clinical practice.