The Gosford Park star, who is married to singer-turned-actress Billie Piper, is appearing in West End play Our Boys, but he is relying on pain pills and osteopathy to get through the shows after he was struck down with scoliosis, curvature of the spine.
Fox's condition may require surgery in the future if it gets worse, but for the moment he is numbing the pain with medication - and he is taking the setback in good spirits.
He tells British newspaper the Sunday Express, "I've even given my pills names. I've just had two Alices and one Frank. Frank is a real bruiser."