Arthrosis usually starts with damaged joins: lack of movement, but also obesity, and malformation cause cracks in the cartilage. These cracks become bigger with outside forces leading to even more brittle joins. Simultaneously, the joins are inflammed which advances the decomposition of the cartilage.
During these repairs, the structures of the particular bones is changed with the consequences that the fitting form of the particular joint is lost - more damages are already foreseen. Also the joints of the vertebral bodies can be affected by arthrosis. This mostly starts with a degeneration of the vertebral disk: if the distance between the vertebral bodies become smaller, more strain is put on the vertebral joints. This can cause heavy, motion depending back pain.