A needle for invasive medical use includes a long extended cylindrical needle shaft having an axis and an outer surface area, with a short shaft end at a first end of the shaft with a beveled tip with a pointed end, and a needle hub attached to a second end of the shaft including a device to indicate the location of the shaft end during use inside a body. The needle has a flexible joint with a notch within the shaft at the beginning of the shaft end. The device is a displacement sensor for detecting a displacement of the shaft end relative to the rest of the shaft resulted from a force applied to the shaft end when the needle hub is moved and a signal conductor to transmit the detected signals. The invention further describes a needle assembly comprising such a needle and a syringe attached to said needle hub, whereas an evaluation unit is connected to the signal conductor.