Is it permissible for a woman to wear trousers due to health conditions that prevent her from wearing skirts and hinder her movement, knowing the Sharʿi ruling on trousers and that they are impermissible because they reveal body contours and involve imitation of men, and knowing that the necessity is only in the winter season?

It is not permissible for a wife to wear trousers and appear in them before non-mahram (definition) men, even if they are specifically for women. The claim that they impede movement or that they are due to cold and rain is unacceptable, as there are other options for women's clothing that provide comfort and protection from cold and rain. However, if she wears them under a jilbab or in front of mahrams, and they are wide, then there is no harm.