Burgers at sit-down restaurants are often pinned or skewered with garnishing sticks, toothpicks, and the like, to keep the burger together as it's carried out to the table. It prevents the bun "lid" from falling off the burger (especially with American-style large burgers with thick-cut vegetables or fried toppings).
I wouldn't say knives as skewers are common. Just going by Google Image Search results, one might be inclined to think that something like Burgers as Garnish for Bloody Mary is common:
But they're not common. Unless you reduce the search area to "Milwaukee or Minneapolis baseball parks, and specialty bars in Vancouver that try to go for the most ridiculous Bloody Caesar / Bloody Mary concoctions".
Yes, I posted this answer just to include the ridiculous drink garnished with junk food.