Is it permissible for us to see our mother's legs above the knee due to a skin disease?

The jurists have unanimously agreed on the prohibition of a man looking at the 'awrah of his maharim (female relatives with whom marriage is perpetually forbidden), which is between the navel and the knee, absolutely. It is not permissible to obey one's mother if she asks to look at these areas, as there is no necessity for it. One must, however, explain the religious ruling to her with gentleness and kindness. Looking is permissible only when there is a necessity, such as for medical treatment.