Physical Danger
Well, to be blunt, you run the risk of getting super grossed out. But even if you have a strong stomach, you'll run some pretty obvious risks of getting sick when your patient gets something contagious. Cold and flu season will totally be your worst enemy (source).
You'll also be handling a lot of needles, drugs, and sterilizing chemicals but you should be fine as long as you follow the strict, standardized guidelines (source).
The true risk is back injury. You'll be doing a lot of standing and lifting of your patient from wheelchair to bed, bed to toilet, etc. You'll likely be saying "Oh, my back!" more than any old person you treat (source).