What causes Gregory House's chronic limp in House M.D.?

Gregory House's chronic limp is caused by a quadriceps muscle infarction.

In the series backstory, a blood clot blocks circulation in House's thigh, causing infarction in the quadriceps muscle. The damaged tissue is not removed promptly, and House is left with permanent muscle loss, severe pain, and the limp for which he uses a cane.

The injury also explains House's dependence on the opioid painkiller Vicodin. His pain-management problems become a continuing character and plot element, affecting his judgment, employment, and relationships. The physical injury is therefore not just a visual detail; it shapes the show's central conflict between extraordinary diagnostic ability and self-destructive behavior.

The condition is often incorrectly summarized as a broken leg or a generic muscle injury. House did not acquire the limp from a fracture. The specific event is an infarction of the quadriceps muscle, resulting from interrupted blood flow and subsequent tissue damage.