It does depend on how old the jostaberry is. If it's less than 3 years old, I'd leave it alone apart from removing anything dead, damaged or diseased.
I treat mine mostly like blackcurrants, which means that a third of the oldest stems are cut down to the base each year in winter. They fruit on wood that grew the previous year or year before that. If you leave the stems to get older than about 4 years, they get leggy and don't produce as much fruit.
