Spondylthesis is when one vertabra shifts off the one below. Image a stack of blocks but then one block sticks out further. Makes the whole “stack”, aka spine, more injury prone and affects load bearing. Spondylethesis is graded based on how far the vertabra has moved off the other. I believe it’s 1-4 and it goes by % of vertebra shifted off the one below. Spondylethesis is not good bc it puts pressure where it shouldn’t be and if VERY bad can result in serious injury to the spinal cord.