How do you deal with severe arthritis in the knees on a day to day basis?

Stay active. Arthritis is like rust in the joint. Activity and flexibility can help keep the joint mobile and lubricated. Unless contraindicated, tylenol (acetaminophen) or Motrin can be very helpful. Some people get good relief from glucosamine chondrointin, but evidence is conflicting. Talk to your doctor, an injection of cortisone or a series of injections with medications like synvisc may also be helpful.
Few things. First, weight loss if overweight (dramatically lessens load on arthritic knees). Gentle progressive walking program or physical therapy if muscles deconditioned. Pain medications (over the counter or prescription rx). If rx fail, cortisone injections or hyaluronic acid injections into the knees. Last resort is knee replacement surgery.