What is the title of the House, M.D. episode that reveals how House injured his leg?

“Three Stories” reveals how Gregory House injured his leg in House, M.D. The episode uses three parallel medical stories, with House teaching students while gradually revealing the truth about his own past.

House suffered an infarction in the quadriceps muscle of his thigh. The condition was initially misdiagnosed, and the resulting damage eventually required surgery. House rejected amputation, but the treatment left him with chronic pain and a permanent limp.

The episode is notable because it connects House's physical condition to his personality and addiction. It also shows that his medical brilliance does not make him immune to diagnostic error or the consequences of delayed treatment.

“Three Stories” is the 21st episode of the first season. It won a Primetime Emmy Award for Outstanding Writing for a Drama Series, making it one of the most celebrated episodes of the show.