Hi. Supplements to a dog's diet such as Glucosamine and Chondroitin Sulfate, Omega Fatty Acids, Vitamin E, Selenium, and MSM (Methylsulfonylmethane) all assist in decreasing inflammation and improving the body's ability to repair and strengthen tissues. Supplements, however, will not reverse structural changes in a joint such as torn cartilage, calcium deposits and advanced scar tissue.
It could therefore be that the Glocosomine isn't working because it can't remedy the particular problem your dog has.
Tony
My dog weighed 28-30lbs and the correct dose for her was 500mg Glucosamine per day. The vet said the 'human' Glucosamine was fine to use, so long as the dosage was correct for the dog's weight.
So it depends what your dog's weight is, how much you can increase the dose.
As far as I can make out, dogs (and humans too) respond differently to Glucosamine. With some there are great results, and with some, not much improvement.
You could mention this to your vet perhaps. There may be other natural drug-free remedies which would help, even alongside the Glucosamine.