If you want to know if there is arthritis you would need to have an x-ray done. If you want to lessen the symptoms you could try PROMAXOL. It helps to decrease pain, inflammation, and stiffness and stimulate healing. Initially I would give a half dose with breakfast and again at supper. After improvement is seen you can decrease to a whole dose once daily. For longer term management you can switch to ARTHRO-IONX.
I would also use PROBIOTICS, MSM, Vitamin C, and OMEGA 3,6,9 to reduce inflammation and strengthen the body. What type of food and water are you giving? The selection of food is important in arthritic symptoms. What breed is your dog?
I would also suggest an evaluation by a veterinary chiropractor. If a correction is needed, that can help with better movement. Acupuncture is also helpful.