As these have been my words terrifying you, I will happily put them into perspective. After all, I am double-jointed myself with more than two decades on the mat (Judo/BJJ mainly) and in training to become a physiotherapist.
The main question should be: What is your goal in BJJ?
If it is for recreational reasons and/or a little bit of self-defense and confidence, I see no problems. If it is going hard and often and doing competition, I'd advise against that.
Everybody has to use the muscles and move in odd ways sometimes to keep their joints healthy. This is just as, if not more important with this condition. The problem is that due to ligaments being more elastic than usual, the fascia glue together and the muscles overstress much faster given consistent one-sided use of the joints or consistent external stress in order to stabilise the joint and make it "fit" for how you use it. This leads to the joints being pressed together by cramping muscles in certain positions and eventually, the cartilage dies since it only gets nutrition through liquid flowing in when it is properly freed from pressure at any given point. Therefore, ypu need to use the full range of motion but your body works against that since it wants to keep things together, as it were, because of weaker ligaments. As if that wasn't enough, external stress also more often directly damages the passive structures which are much slower to heal.
The consequence for you is not that you should not train BJJ. It is that you should
- Tap rather sooner than later
- Keep it smooth and try not to go full strength.
- Avoid partners going all-out and competition.
- Plan to do extensive stretching and/or yoga/pilates to counter the potentially one-sided load and moving angles of certain joints. This should include a full mobilisation of as many joints as possible in as many and great angles as possible.
The latter should be what everybody does but is even more important for you. If you do not keep your fascia and muscles smooth, you will eventually be in pain and have degraded joints.
And this is true no matter whether you do BJJ or not.
