Clunking when turning steering wheel

My vehicle has about 120,000 miles on it. In the last week or so, it has developed an issue where it makes a "clunk" noise every time you turn the steering wheel. It makes the noise at regular intervals about every 1/2 turn of the wheel, in other words, it is not just when you first start to turn (as if maybe there was some play in the joints), but it will "clunk" four or five times when you turn the wheel all the way one direction or the other.

The noise is louder on the passenger side than on the driver side, and you can feel it in the steering wheel.

Anybody have any insight about what this might be?

Thanks!