hands...

The first thought I had when we see Kate's arthritic hands is that it confirms the description that Adam gave of their mother - that her own mother had arthritic hands and Kate was always worried she would likewise be afflicted.

But you are probably right that there is a deeper meaning. Arthritic knees, for example, would not have symbolic potential. So hands are a way we touch the world, and Kate's are deformed.

There is also the theme of passing good/evil through generations (more of that in the book) and it is interesting that Kate inherited her mother's affliction. I can't remember how Kate's mother is portrayed in the novel.

As to why she wears gloves - the "reveal" makes it more interesting than if her hands were easily observable, but it may also be her attempt to cover her deformity. For all the evil she has done in her life (again, the novel has more) she tries to appear to be normal - even though she is in a sketchy business.

Thanks for asking this question. I'd like to hear other interpretations.