Anyone have experience with trekking poles?

My dad has requested a pair of trekking poles for Christmas. He is getting older and now experiences pretty bad knee/leg pain on backpacking trips. He intends to use only one, but I will buy two as mostly come in pairs, I might use one some day, and they're also doubly effective in pairs, so he may just end up using both.

For the sake of example, I'm looking at the Black Diamond Trail Back Poles for $47.50, the Black Diamond Contour Elliptical Trekking Poles for about $96.

My principle concerns are length; my dad is maybe 6'2" and will need something that accommodates his height. I imagine most poles do extend to a length suitable for persons of this height?

I'm not too worried about build quality or strength given the reviews on amazon seem to indicate that both of these poles are functional. My dad doesn't go on more than 2 trips a year so these thing won't be getting too much use.

Finally, is it worth spending the money on an anti-shock feature? I think that going from using no poles at all to using basic poles would already be a huge improvement in stability and shock absorption, so I'm not convinced the anti-shock feature would be going much farther for the money.

Update: I'll probably be going with the Trail Back Poles thanks to the brief review from u/sodoesyourface

Thanks again for all of the insight folks. All of your comments have been helpful. I will certainly let him know that he should use both poles and he should watch a video on how to use them.