You don't have to run to lose weight. Just increase the intensity and duration of your hikes. Running well over weight with bad knees is just goingto give you worse knees. If you can start a strengthening program along with your hkes you will get much better results. Lastly, keep a food journal and don't cut calories below 2000 - 2400 or you'll just needlessly suffer, lower your metabolism and make it less likely you will stay on your program.
Best,