According to the Cleveland Clinic, piriformis syndrome causes pain or numbness in a person’s butt, hip or leg. The pain typically occurs when the body’s piriformis muscle presses on the sciatic nerve which results in inflammation.

Piriformis syndrome is a rare neuromuscular condition that happens when the piriformis muscle in the butt presses on the sciatic nerve, according to the Genetic and Rare Diseases Information Center (GARD).

"It's a muscle that kind of clamps down on my sciatic nerve, and it was shooting down my leg," the actress said during an appearance on 'The Drew Barrymore Show'