Most people would recognize the condition under the name "degenerative disc disease." Five % of the population has it and never known it. Other people can have it diagnosed and virtually have no symptoms. And others can have it with variable levels of symptomatic presentation.......pain, numbness, weakness and loss of muscle coordination.......essentially "pinched nerve" symptoms.
As the process progresses various cartilage and boney surfaces of opposing vertebrae are worn away, leading to progressive arthritis and, when severe enough..........vertebral fusion.
However, this is typically a condition that occurs more in an aging population. Mettenberger is certainly not an octagonarian. So we have to look to trauma as the source of the degeneration. In a normal population, spondylosis can be controlled with attentive conservative treatment. Heavily trauma-exposed NFL players are not the "normal population." There is one very important fact that we don't know at this point..........at what anatomic level is the spondylosis located (and how many levels of individual vertebrae are involved). The reason this would make a difference is that if he is experiencing the problem at the thoracic level, affect on performance, likely hood of significant progression, and need for surgery would be quite uncommon. This is not the case for cervical or lumbar spondylosis, which is more likely to be more difficult to treat conservatively, leading to significant loss of playing time, and then eventually to possibly surgery.