When I went to back my car out I heard a sound like I had run over a can

Then it was very difficult to turn my steering wheel? I live in a fairly hilly area with curves. It drove as normal on the road, but when I had to make 90 degree turns the steering no longer felt like I had power steering. I checked the power steering fluid and it looked okay. Any idea on what may have happened to cause this sudden difficulty in making turns?