Really depends on how bad it is what you're wanting to do and the horses motivation
Tbh, I think the fairest thing to do is to pts, you may be able to maintain for a while at a lot of cost and eventually, it'll get worse and be pts anyway. Pts before the horse deteriorates
Navicular is a bone that every horse has, but some horses can have problems in that bone. If the problems are very little than you can control them with specific shoeing and some medication from time to time and you can keep your horse in competitions at a high level. However, in some extreme cases the horse has to do a surgery and can't continue his career.
If a horse has that I would suggest ending jumping or lowering them a lot until it’s 100%
in my opinion it's not worth it but if it can be maintained and you have enough money to pay for it it's ok. The horse just can't go in tight circles or canter very much as it can go lame