Endochondral ossification is a normal bone growth process by which cartilage is replaced by bone in the early development of the fetus. Osteochondrosis is a pathological condition in which normal endochondral ossification, the metamorphoses of cartilage to bone, is disturbed. The disturbance is often due to a disruption in the blood supply to the bone. The result is retention of excessive cartilage at the site as the process of endochondral ossification is halted, but cartilage continues to grow. The end result is abnormally thick regions of cartilage that are less resistant to mechanical stress, as opposed to the stronger and denser bone.

Large and giant breeds, including great Danes, Labrador retrievers, Newfoundlands, rottweilers, Bernese mountain dogs, English setters, and old English sheepdogs are predisposed to this condition.

Source: http://www.petmd.com/dog/conditions/musculoskeletal/c_dg_osteochondrosis

Spondylosis deformans is a degenerative, noninflammatory condition of the spinal column characterized by the production of bone spurs along the bottom, sides, and upper aspects of the vertebrae of the spine. These bone spurs are simply projected growths of bone, usually grown in response to aging, or injury.

In dogs, spondylosis deformans occurs most often along the spine, in the area behind the chest, and on the upper section of the vertebrae of the lower back. Older, large-breed dogs are at highest risk for developing spondylosis deformans. In cats it tends to occur more often in the vertebrae of the chest.

Source: http://www.petmd.com/dog/conditions/musculoskeletal/c_multi_spondylosis_deformans