In House M.D., what was the cause of Dr. House's chronic leg pain?

In House M.D., Dr. House's chronic leg pain was caused by a quadriceps infarction.

House suffered an infarction in the quadriceps muscle of his right thigh, meaning that blood flow to the muscle was blocked and tissue died. Doctors initially considered amputation, but House chose a treatment intended to preserve the leg, leaving him with lasting muscle damage and severe pain.

The injury explains House's limp, cane use, and dependence on prescription pain medication. The series reveals the history gradually, especially through flashbacks and conversations about his former relationship with Stacy Warner.

The injury is often described loosely as a “leg infarction,” but the more specific diagnosis is a quadriceps infarction. It was not presented as a broken bone or a conventional sports injury, and the resulting pain is a major part of House's character.