Here is what wikipedia had to say about BJJ and joint pain:

While many joint locks are permitted, most competitions bar or
restrict some or all joint locks involving the knees, ankles, and
spine. The reason for this is that the angles of manipulation required
to cause pain are nearly the same as those that would cause serious
injury. Joint locks that require a twisting motion of the knee (called
twisting knee locks or twisting knee bars, or techniques such as heel
hooks, and toe folds) are usually banned in competitions because
successfully completing the move nearly always results in permanent
damage that requires surgery. Similarly, joint manipulations of the spine are typically barred due to the inherent danger of crushing or mis-aligning cervical vertebrae.
Certain locks involving the knees and ankles are only allowed in
competition starting at the brown belt. Any competitor from white to
purple belt who attempts any of those locks may be disqualified.

However, most joint locks involving the wrist, elbow, shoulder or
ankle are permitted as there is a great deal more flexibility in those
joints and those locks are safe to use under tournament conditions.
Also, some fighters practice moves whose sole purpose is to inflict
pain upon their opponent, in the hope that they will tap out. This
includes driving knuckles into pressure points,
holding their opponent's head in order to tire out the neck (called the
"can opener" or kubi-hishigi) and putting body weight on top of the sternum, floating ribs,
or similarly sensitive bones. These moves are not true submission moves
- they are generally only used as distractions mostly in lower levels
of competition. They are avoided or brutally countered in middle to
upper levels of competition.

Maybe there is some connection between this info and your joint pain.  It sounds like it does not treat joints well