I read the following in the Transmitter - the newsletter of the Victoria BC Parkinson Society re PD pain and arthritis pain: Arthritis produces pain in joints. PD produces pain in muscles. If you are at rest and someone bends your arm at the shoulder and it hurts, this probably arthritis. If the same person squeezes your arm muscle and it hurts, it is probably due to the PD. Anti-inflammatory medicines relieve arthritis pain; anti-PD medicines relieve rigidity and cramps associated with PD. Although there are always exceptions, the above is a good common sense rule of thumb.