The present invention relates to a device for detecting and monitoring a lesion, such as a rupture, for example, of the anterior cruciate ligament or ACL of the knee, comprising the anterior translation of the tibia relative to the femur using the so-called Lachman test. The device is characterised in that it consists of at least: a substantially-semicylindrical, elongate, concave and rigid part, referred to as a shell (1) and capable of capping the tibia of a patient such that the free ends (2, 3) thereof respectively bear on the lower diaphyseal region of the tibia and on the upper region of the patella, the concave wall of the shell (1) defining a free space with the upper portion of the tibia an inflatable pouch (4) that can be positioned on the convex surface of the shell (1) in the upper portion of the tibia and connected to a pressurised fluid source (5) and means (6) for attaching the shell (1) to the leg of the patient.
