This paper presents a comprehensive review of bending sensors and their classifications. The main focus is on advancements in the design of optical fibre bending sensors based on fibre Bragg gratings (FBGs). Various measurement principles employed in optical fibre bending sensors are analysed, highlighting their respective advantages and limitations. Particular attention is given to sensors utilising long period gratings (LPGs), Tilted fibre Bragg gratings (TFBGs), and multicore (MCF) fibre structures, which demonstrate significant potential for the development of highly sensitive and compact bending sensing systems.