Pain in PD can occur for a variety of reasons. Pain occurs in up to 75% of PD patients; it is typically individualized and does not always correlate to stage.
Tinazzi M, Recchia S, Simonetto S, et al. Muscular pain in Parkinson's disease and nociceptive processing assessed with CO2 laser-evoked potentials. Mov Disord. 2010;25(2):213-220.