What kinds of physical therapy work in arthritis?

Various. Generally low impact, strengthening exercise help.
Low impact. Aquatics, body weight, or resistance bands/ tubing biking, and/or elliptical. Aquatics allow you to perform body weight exercises, but being in water actually reduces the stress on your body due to buoyancy. Once you are able to perform body weight activities then look to add light resistance w/ bands/ tubing.