This was over on FB with lots of comments and suggestions. Here is my take:
That means that, if a body part is lost — for example, in an amputation — or if a body part if not functioning properly — for example, if somebody experiences stiffness — it could result in deficiency doing some kind of activity of daily living: for example, dressing/undressing, putting on — tying buttons/untying buttons from a shirt.
There may be a couple of other possibilities there at the end. And, for the record, nothing makes this sentence look good. 🙂