Abstract: Provided are systems and methods relating to a modular orthosis system for an orthosis of the lower extremity, which modular orthosis system simplifies an individual fit to the respective patient and his loss of function, and, during the course of the therapy, can be fitted with direct consultation of the patient to changed circumstances in an interdisciplinary manner. A particular exemplary advantage of the orthosis system is that the therapist, together with the patient, can test the position of the support spring (dorsal vs ventral, medial vs lateral) and also different spring strengths. Thus, the orthosis can be fitted to the patient in a simple manner.