Dyskinesia is the writhing motion that most people associate with Parkinson’s. It is a side effect of the “gold standard” treatment for PD, which is a drug with the brand name Sinemet. Sinemet is basically dopamine, which is what our PD brains have stopped making.
The best example that you may have seen is Michael J. Fox, of course. When you see him interviewed, he’s moving around like a man possessed. That’s because he took his Sinemet and the levels (of the drug, and the stress of the interview) are too high. The alternative would be to see him in an “off” state, which in his case (and mine) means uncontrollable tremor, stiffness and rigidity, stooped posture and (for him) freezing — like a statue, while walking or getting out of a chair.
Most people associate PD with dyskinesia, but that’s actually incorrect. PD is characterized by a lack of movement. I used to fluctuate between those two poles six times a day — the times when I had to take Sinemet. And that’s a different explainer altogether!