from work -
static postures/positions, overuse, repetition, speed, strength and 10 hr workdays x 15 yrs.

My part of the "blame" was my drive to have the best quota numbers and low reject rates.
Got me very good raises but really did a number on me took about 3-4 yrs to get back to a mild chronic stage.

The fact that I have some hypermobility played a part too, but it's not usually noticed or mentioned until after someone is injured with multiple RSI type problems.