Hello, and thanks for writing in. I'm sorry to hear that this is going on with Bear. It's hard to see our friends in pain and not able to get around well.
A shoulder injury could possibly cause what you are seeing, but I'm also concerned about a disc problem in the neck. A disc problem in the lower spine would only affect the hind legs, but if you are seeing problems in the front end at all, then I would be more suspicious of a neck problem (disc problem), since this is common in small dogs, and can possibly affect all four legs, and cause pain anywhere from the neck backwards. If the prednisone (steroid) and robaxin (muscle relaxant) are not taking complete care of the problem, I would recommend further diagnostics (i.e. myelogram, CT scan or MRI, consult with a veterinary surgeon), to see if there is more going on (herniated disc, fibrocartilagenous embolism, growth, etc.). I'm also concerned that Bear is not being treated with any type of pain reliever. Prednisone and other steroids are not used much anymore for back problems. More commonly now, drugs called Non-Steroidal Anti-Inflammatory Drugs are used, since they help with swelling and inflammation (like steroids), but they are also very effected for pain relief, which it sounds like Bear needs at this time! So, rest is very important, but at a minimum, I would ask your veterinarian to prescribe pain medication for Bear, and if he is not responding, he really needs further diagnostics to see if there is more that is needed for treatment. Also, sometimes surgery is needed to get the problem under control, especially if a disc problem in the neck is present. You can read more about cervical (neck) disc disease HERE.
I hope this is helpful. Please let me know if I can help further.