Hand injury

I'm 40 years old, 6'3" and 220lbs.. I started working out on a 100lbs heavy bag about 2 years ago. After about 4 months of 1/2 hour a day, the back of my hands started hurting. It got to the point where I could not even hold a tennis racquet. I went to PT and they said it was tendinitis. I laid off for a year now and just started again 2 weeks ago with a portable heavy bag (water filled bottom) as I thought it would be less resistance. The back of my hands just started to hurt again. My wrists are fine and my knuckles are fine. It's the tendons that hurt. I wrap and use bag gloves. Any suggestions?

'what do you do b4 you start working the bag?
do you have a decent warm up?
decent stretch, holding it 15 sec and do everything twice?
losen up your joints and dont forget to rotate your wrists witch is important.

after this you should start of easy on the bag, building up the power.
since your a big guy, your hands and wrist get alot of impact witch they are not used to,
so build up slowly with the power punches.

you might as well consider using sparring gloves on the bag, the heavier ones (16+ oz).
the offer more protection to your hands than regular bag gloves.

and after you finish punching the bag.
do some easy and very lose shadowboxing to cool down.
then rotate and losen up your joints again.
and stretch all the muscles twice 15 sec.

this should keep those hands from hurting.
hope this helps

also it could be what the bag is stuffed with some bags are stuffed with strips of neoprene that have some good cushioning properties and ive seen soem stuffed with just like cheese rag material if its stuffed with something too hard than perhaps it could be over stuffed.. but this is all just my experience because i stuff bags myself.. and old clothing seems to work best for me ;D