According to official Sonic Team polls, Knuckles is the fourth most popular character in the series, following behind Tails , Shadow , and Sonic.  Complex listed Knuckles as their eleventh most wanted character in the next Super Smash Bros. game.  Game Rant include Knuckles on their list of "Top 10 Third-Party Characters that Could Appear in the New Super Smash Bros.", commenting "This punch-drunk brawler knows how to serve up a buffet of knuckle sandwiches, and there’s no question that he’s one of the most fitting characters to occupy a spot on the roster". 
Knuckles is also shown to have sharp reflexes and acrobatic skills, enough to let him do special tricks and movements while in mid-air, pull off various Spin Attack maneuvers at high speed, and grind along rails just as fast as Sonic while doing tricks and evading obstacles.  Additionally, Knuckles can jump several stories into the air from a standstill position.  While not being quite as acrobatic as Sonic and Shadow , Knuckles makes up for his lack of agility through his wide range of movement abilities. By stretching his arms and legs outwards while airborne, Knuckles can catch the air under his dread-lock-like spines to ride on air currents,  allowing him to expertly glide long distances through mid-air. Also, by using the spikes on his fists, Knuckles can scale any kind of surface with ease.
The history of the game begins with the release of the Mega Drive game Sonic & Knuckles . The unique cartridge featured "Lock-On Technology" and allowed players that also owned the game Sonic the Hedgehog 2 to link the two together and play the game through as Knuckles instead of Sonic. However, partly because of a poorly matching colour palette, no such feature was included in the first Sonic game (instead, attaching Sonic 1 to the Sonic & Knuckles cartridge unlocked the full version of Blue Sphere).