In full disclosure, I am definitely no auto mechanic. However, I have been told that cars tend to run better when they are driven. A car left idle for long periods of time may run the risk of belts becoming corroded, carbon building up in the engine, and wheels getting flattened or jammed up.
In many ways, the same holds true for people. The Arthritis Foundation considers exercise to be, “the most effective non-drug treatment for reducing pain and improving movement in osteoarthritis.”