Objective evaluation of antero-posterior and rotatory laxity of the knee is a critical issue in anterior cruciate ligament (ACL) research. Th is is essential to allow surgeons to rigorously evaluate the outcome of the diff erent available techniques. Furthermore it will make it possible to carry out advance predictions of which patients can benefi t from a particular approach, i.e. partial reconstructions, single- or double-bundle techniques. Th e ideal method should be able to assess anatomic and functional features of the ACL-defi cient knee, besides being accurate, reproducible and cost-eff ective. Th is is an overview of the most recent achievements and the scientifi c-technical considerations in this particular area of research. Th is chapter presents the advantages and limitations of robotic systems and manual instrumented devices compared to manual tests that are commonly used in the clinical setting. It also highlights the Porto-knee testing device as a new tool to assess laxity in ACL-defi cient knee during magnetic resonance imaging. Insights of intraoperative navigation-assisted tools are also considered.