I would be concerned for a proximal suspensory issue - if her hocks are clean I don’t see why she’d need them injected. Trying Adequan is not too invasive and is worth a try I’d think though.
My guy has proximal suspensory injuries and SI soreness. I’d say these two are often related.
I wouldn’t inject the hock because if it suspensory, the injection trickles down and makes the suspensory feel better. It is short lived and the horse can end up causing a bigger injury consequently.
An SI injection I’ve done for my horse and it make him more comfortable. Even if you resolve the root of the problem, it’ll take some time for that SI soreness to go away. Sometimes you just need a one-time injection to help with inflammation.