To determine if your dog needs a joint supplement, evaluate their current diet and observe for signs of joint discomfort or mobility issues. If the diet lacks essential nutrients for joint health or if your dog shows symptoms like limping or stiffness, consider joint supplements.To determine if your dog needs a joint supplement, evaluate their current diet and observe for signs of joint discomfort or mobility issues. If the diet lacks essential nutrients for joint health or if your dog shows symptoms like limping or stiffness, consider joint supplements.