Hugh Hefner Photo Shows Mogul Frail Months Before Death

Hugh Hefner was in failing health for years, and he steadily deteriorated in the final months of his life.

This pic was taken in January ... inside the Playboy Mansion. Although Hef was frail, using a walker to get around, he still hosted movie nights and invited people over.

TMZ broke the story ... Hefner got a back infection 2 years ago and that became the linchpin for a variety of ailments that ultimately led to his death.

Hefner died Wednesday night at age 91.