She should certainly have an examination to determine the reason she can't walk, caring for anyone with limited mobility is exponentially harder. My mom began falling in her 90's primarily due to weakness from years of being mostly sedentary and a diminished appetite that led to frailty, no double the pain in her knees and hips contributed as well.
My family member has plates and screws in one leg and was wondering several years ago if there was a problem with the metal having shifted or was compromised somehow. I sent her to an ortho doc who ordered a simple xray to assess this. Once determined her plates/screws were OK, then other causes for her pain and mobility problems could be looked at.