The invention concerns a variable-length crutch 1 comprising a main body 2, a foot 5 extensible and retractable with respect to said main body 2, and an actuator comprising a motor 6 with a rotary output shaft 9 and a worm transmission in order to convert a rotation of said motor shaft 9 into a linear movement of said foot 5 with respect to the main body 2. The worm transmission is irreversible. The actuator also comprises a programmable module 8 controlling the motor 6 and a sensor 10 for extending the foot 5 with respect to the main body 2. The module 8 is connected to said motor 6 in order to control the extension and/or retraction of the crutch to a preprogrammed length and to stop the motor 6 when said length is reached.
