If you have a joint account, the person who shares the signing authority with you is not liable for your debt (unless he or she is liable for some other reason). The joint account is an asset of your bankruptcy estate, but even this does not mean that the bankruptcy trustee can take all of the funds from it because of your debt. If you can provide proof that only a some of the money is yours, or even that your name is attached to the account simply for the purpose of convenience, then the money can be freed from the reach of your creditors.
While this may seem like a possible way to hide money from creditors and bankruptcy court, it will be investigated by the bankruptcy trustee and could result in the ruling that the transfers were fraudulent. In this case, the person with whom you share the account will be liable for the amounts and have to return the payments.