Cats can be very sensitive to certain types of pain medication such as non steroidal anti-inflammatory meds. But these drugs can be given cautiously for short periods of time. We also use narcotics such as Buprenex to help relieve pain. Massage, acupuncture and spinal manipulation are very useful to help relieve chronic pain such as arthritis.
So if you suspect your kitty is hurting speak to your veterinarian to see what options are available to help.