The employee was in the mezzanine pulling tires for a vehicle that was being serviced. While walking to the mezzanine stairs, he stepped inside of a tire. As he raised his foot to walk, his heel got caught causing him to lose balance. He landed on his right knee. The employee felt he could continue working and did not request medical attention. He worked the remainder of his shift. Three weeks later the employee was admitted to the hospital for an infection to the injured knee.