Mikolette/Getty Frozen shoulder can make simple tasks – such as lifting your arm, sleeping on your side, getting out of bed, putting on a bra, driving or playing with your kids – painful and challenging. This condition usually starts with pain suddenly developing in the shoulder and stiffness. Over time, the pain and stiffness get worse. It can drag on for months or even years. So, what causes frozen shoulder? And can it be treated? What is frozen shoulder? This shoulder condition, also known as