It's the last episode from when he was a regular character. (he had a few guest appearances later)
He goes on an away mission with Picard and they crash land on a desert planet. In one scene as he is walking towards Picard it's quite evident. I have the episode saved on my DVR.
This is from the scene:
http://i1.ytimg.com/vi/ioAq7BqG4Eg/hqdefault.jpg
but you can't see anything in that pic and you really need to see the video to appreciate it.
Edit:
Found it! but the quality isn't very good:
clear vpl - YouTube