In this monograph we approach the ACL deficient knee from a different perspective than those of the previous classical ways. The common approach is the analysis of closed compartments; anatomy, biomechanics, physical findings, imaging, surgical treatment and rehabilitation. Our approach is completely opposite. We are focused on questions, controversies, problem analyses and problem solving, besides analyzing the possibility of prevention. Therefore, in each chapter, the biomechanics, anatomy, etc. that are relevant to the topic are reviewed. There are chapters where highly specialized surgical techniques are presented (acute ACL repair, double bundle reconstruction, chondral lesions treatment or meniscal transplant). These chapters are written by internationally renowned specialists that are pioneers in the topic analyzed. Another interesting aspect of this book are the step by step surgical techniques videos, that will allow a knee specialist to perform the technique presented by the author. Moreover, the videos will include anatomy and physical therapy techniques.