The Fireball (1950)

Johnny Casar (Mickey Rooney) runs away from a home for wayward boys, tired of being teased about being short and a poor athlete. He soon finds a pair of roller skates and is befriended by Bruno Crystal (Ralph Dumke), who allows him to wash dishes at his café, while a priest who runs the home, Father O'Hara (Pat O'Brien), secretly keeps an eye on him.
A traveling roller-skating team takes an interest in Johnny after he shows some aptitude. He clashes with Mack Miller (Glen Corbett), a cocky champion, and falls for Mary Reeves (Beverly Tyler), another top skater. Johnny ends up featured in grudge matches against Miller, where they take turns one-upping one another.
As his fame grows, Johnny becomes every bit as arrogant as Miller and more. Life takes a bad turn when he is diagnosed with polio. A long period of physical therapy follows, until a wheelchair-bound Johnny tries to get his life back on track.