Hello Salma,
This may sound kind of strange, but in addition to massage and range of motion, sometimes just placing your hands around the area that is painful is helpful, especially if you do this with specific intention of facilitating pain release and relaxation. Try to imagine that you are bringing into and through yourself white, 'healing' energy, and transferring that energy from your hands to your father. If this is uncomfortable for your father, you can also do this without touching him, but by placing your hands a few inches away from his skin. This is called energy work, and it is a type of bodywork that is often used on people who cannot tolerate actual massage.
Best wishes,
Sharon