All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
According to the preponderant view of the scholars the limits of the ‘Awrah of a woman with her Mahrams is her entire body with the exception of her limbs, like her head, her arms and her feet. They are not permitted to see from her body other than this. Therefore, it is not permissible for you to massage your mother’s knees and you are not permitted to obey her in this respect because there is no obedience to a creature in disobeying the Creator. Rather, you should refrain from such a thing even it was permissible as a way of protecting oneself against any forbidden means which leads to something forbidden especially at these times in which afflictions are so many.
In addition to this, any female Muslim relative of hers could give he massage, like her daughters, her sisters or any other woman even if she is not a relative.
Allaah Knows best.