In the King's Day parade, the crown prince makes an appearance, waving and "using a cane to steady himself" (45.46). When Sadima asks Franklin if the prince is lame, he answers: "They say it was an accident… A horse fell beneath him, trapped his right leg. But he has limped like that since he was a toddler, Somiss says. He is kind and slow-witted. It worries the royals a great deal" (45.48). Somiss would know—he's his brother.
If Somiss and his family are anything to go by, royalty in Limòri is all one huge power game. So it makes sense that people would talk about the crown prince in terms of whether he can be useful or not to them.