It's simple: If you can work a faucet with a closed fist, it's suitable for a range of people, including those with severe arthritis. (The same applies to door knobs and cabinet and drawer knobs and pulls.) An offset single-lever faucet is ideal because it can be operated with just one hand and doesn't require the user to reach so far behind the sink. You can also opt for motion-sensor faucets that activate when you wave your hand under them, such as Kohler's
Tripoint Touchless Electronic Faucet.