Rehabilitation exoskeletons are becoming a reality, promising to expand techniques and therapeutical methods to help people affected by mild to severe motor dysfunctions due to incidents, traumas, surgery, or aging; and to reduce the economic and social impact associated with these disorders. However, the offered flexibility, which would allow patients to use exoskeletal companions in daily life, must come to terms with the conflicting requirements, such as power-vs-weight and functional hardware design-vs-ergonomics. Despite the encouraging results, many researchers still agree on the prematurity of the field and, therefore, in designing exoskeletons without a specific market, human, and motor dysfunction target. This Thesis analyzes some control strategies implemented in exoskeletons for lower-limb rehabilitation.