Gout/polyarthritis/rheumatisum. what are differences?

Several: Gout is one type of joint inflammation. Arthritis describes all of the 105 types of joint disease, and rheumatism is a very old term used before modern diagnostic techniques were available.

Joints affected: Gout is usually a monoarticular problem, meaning it occurs in one joint. 75% of the time it affects the big toe joint. It can occur elsewhere such as the knee, elbow, or ears. It tends to occur at distal extremities where the temperatures are coldest. Polyarthritis on the otherhand affects more than one joint at a time. Rheumatism is an older term that is not used so frequently anymore.