Lung mets are much more common especially if the dog does not undergo chemo so I think that most of the attention goes to the lungs.  My oncologist told me that dogs that had amp plus chemo were more prone to spinal mets or mets to another leg.  It is also very hard to diagnose spinal mets since the symptoms often show up before the lesion can be seen on an xray. Only an MRI or CT scan could pick those up and the these tests are costly as well as require anesthesia.  Even if diagnosed the prognosis is very poor so that makes things harder.

I have a patient here (Rottie had amp in May 2009) that started walking funny last month but xrays were normal.  I suspected spinal mets and she actually responded to Pred for a few weeks but just had to be put to sleep this week 🙁  This dog did not have any chemo and her lungs were still clear so sometimes the cancer just goes where it wants to.

Pam

No, arthritis involves the bony process on the bottom part of the vertebrae whereas the mets involve the area higher up within the vertebrae near the spinal cord.  Many dogs have spinal arthritis without any symptoms at all.

Pam