The spine is quite complex. I start here with the basic understanding of how the bones should move for good posture and good mechanics.
To answer these questions, it is helpful to have a general understanding of how the muscles and bones work. To be able to see which direction the bones are moving in and to know wether or not the movement is correct. With this knowlege you will be able to bring out the best in your horse and lessen your chances of injury.
I have separtated the spine into two different functions so that it will hopefully be easier to understand. First I am going to talk about what I call the power of the spine. This is how the spine lengthens from head to tail. The thorasic vertebra to the atlas go forward, and the lumbar vertebra to the tail go backward.
The second function is the movment of the spine. This is how the body collects itself.
C6/7 and the sternum engage up and back into the body.
T10 engages up and splits its power to lift the back and fan the withers open.
The TL junction engages to lift and separate the vertebra so that the thorasic power goes forward and the lumbar vertebra goes backward.
C4 engages up toward the topline and creates the arc of the neck. One half of the power goes to the head and the other half goes to the withers.
The atlas opens the poll so that the head can properly swivel and flex.
The LS junction gives the hind end the ability to engage the iliums to lift at the points of croup, drop at the seat bones, and swivel.
The SC junction allows the tail to move as needed for balance.