What caused Gregory House's chronic leg pain in House M.D.?

Gregory House’s chronic leg pain was caused by a quadriceps infarction in House M.D.

The infarction was a loss of blood supply that damaged muscle tissue in House’s thigh. Because the injury was initially misdiagnosed, much of the quadriceps became necrotic before the correct condition was recognized. House chose a risky treatment that removed the dead muscle while preserving his leg, leaving him with permanent pain, a limp, and reduced muscle function.

The story is revealed progressively rather than explained in the pilot. House uses a cane and takes Vicodin to manage the consequences, but the medication does not cause the original leg injury. Viewers sometimes misidentify the condition as a nerve injury, bone fracture, or ordinary surgical complication. The infarction is central to House’s physical characterization and to his complicated relationship with Stacy Warner, who was involved in decisions about his treatment.