Dr. Duncan Lascelles, a famous veterinary surgeon and pain expert, and Dr. Margaret Gruen, a veterinary behaviorist, tackle chronic pain together at North Carolina State University College of Veterinary Medicine. What are the clinical signs of chronic pain in cats? Does their behavior change? Did you realize that 60-90 percent of cats between 6 months and 20 years have symptoms of degenerative joint disease? Of those cats, 45% have pain.