This chapter has well written text and 9 well illustrated diagrams and pictures showing biomechanics of spine. Historical background, terminology, Cartesian co ordinate system, deformation mechanics, Junghans motion are described in detail. Limits and representations and range values of movement of thoracic and lumbar spine are given in tables. Biomechanics of spinal implants and bone grafts are explained in detail. Description of maintenance of spinal stability by muscles, neural control is the highlight of this chapter. 188 references are given for further reading to conclude this chapter.