The device applies to crutches wherein are provided two telescopic tubes (6, 7) which, on the one hand, make possible adjusting the effective height of the crutch and, on the other hand, absorb the impact of the crutch to the ground, the device consisting of a bush (13) which is fitted to the upper extremity of the lower telescopic tube (6) and which has an elongate side hole (15) wherein a pin (11') can play and is secured to the upper external tube (7), precisely through a pair of orifices (12) drilled in said tube so that the length of the elongate orifice (15) of the plug limits the relative motion between the two tubes (6, 7) forming the strut (1), said elements being maintained at a maximum distance from each other by means of a spring (10) positioned between the plug (13) and the second pin (11) of the upper and external tube.