Your seat doesn’t look overly low, but as suggested, I think it’s worth a try.
The short answer, is NO, in general unicycling doesn’t overly stress the hips and it’s not like every rider will develop this problem. Unicycling does stress lots of muscles, and more than anything uses stuff that you may not have used ever in your life (over many many years if you’re no longer a teenager).
Beyond that, I think there are two possibilities:
- you have some kind of pre-existing injury or generic weakness in this area and your hips simple can’t handle so much stress. In his case, you would just have to find the limit and not exceed it, and otherwise try to strengthen other muscles to compensate.
- probably more likely: like most sports-related overuse problems, you did too much too fast. As the muscles and ligaments are stressed in new ways, the body naturally strengthens them (this actually occurs by damaging the muscles by creating little tears in the fibers, which the body then rebuilds stronger), but this takes time only occurring gradually and you can’t do too much or the damage is too great that the body cannot handle it.
For a totally new use/movement/stress, it can take the muscles a few months of training to build up strength and the ligaments take even longer (e.g. this is while joggers get shin splint so often, from increasing running too fast and the ligaments get overstressed). I forgot the exact “number”, but in general only increase training distance/time by 10% per week. This means if you’ve never stressed your hips like this, then on the first day, you should only do it for maybe 5-10 minutes, and then let your body recover for 2-5 days, then increase another 10%. If you have no reaction, meaning pain or swelling, then continue and maybe increase a bit more. At the first sign of too much, reduce and allow 3-5 days of recovery.
While no requiring ice, I’ve presently got the same thing with overdoing it: I’ve ridden my 36er 2+ hours/day the last 5 days, with yesterday being an awesome muni ride. I have an ACL-reconstruction in my right knee and today my knee is swollen. Muni with the 36 is just huge on the knee stress and I have to let the knee recover. The good news, is that next time I should be able to do a little bit more. Maybe not a lot more, but just a little.
Sounds to me like if you really want to do more unicycling, it should be possible and it should just be a matter of finding out how to train and build your strength gradually and never overdoing it.
As an argument to your wife, you can rightly say that in the end it will make you way way fitter, stronger, healthier and injury-resistant (not to mention happier and more balanced).
Good luck and Hope that helps!