Hi, I can relate too.  I practised ITF style TKD in the 70s/80's,  then karate in the 90's and through to 2013.  Now I am 62 and have restricted hip mobility and back issues, but I feel drawn to join a TAGB TKD club where I now live.  I think I have to accept that rank progression may be limited,  butbthatvwon't stop me loving it (as long as I can make it through each lesson!).  Good luck but listen to your body....😊