The British driver locked up as he entered the pits during the second round of stops and slid towards his right-front tyre changer.
King’s Rahal Letterman Lanigan Racing No 42 struck the waiting rear tyre, which in turn ricocheted into his own mechanic at the front of the car.
The crewman went down clutching his right leg and received medical attention while prone on the tarmac.
He was then carried out of pit road as the rest of King’s mechanics strapped on new tyres and sent him on his way, with NBC broadcasters later reporting the mechanic is awake, alert and his injuries are not life-threatening.
The 25-year-old was handed a drive-through penalty for the nasty incident, sending him to the back of the field in the 103rd running of the Indy 500.
It is King’s first appearance at the flagship race, having completed a debut IndyCar season with Ed Carpenter Racing in 2018.
Simon Pagenaud led this year’s Indy 500 from the off in overcast conditions at the Indianapolis Motor Speedway while Colin Herta was an early retirement due to gearbox issues.
Kyle Kaiser also crashed out on lap 71 after getting on the marbles out wide, triggering a safety car while Ben Hanley was another to suffer an early exit.
There was more drama in the pit lane when James Davison and Helio Castroneves came together as the former dived towards his crew.
The two cars collided, causing waiting tyres to be fired across the road – thankfully avoiding all the mechanics.
Castroneves was handed a drive-through penalty after spinning Davison sideways.
The Brazilian is a three-time winner at the Brickyard, while former winners Will Power, Scott Dixon and Takuma Sato are also in the mix.