Had tennis elbow on and off for number of years and docs gave anti inflammatories or told me to stop what hurt – not much use.
About a year ago I started doing heavy weight training and build up arm strength as much as i could suffer at the gyme, within six months much improved, a year later it rarely bothers me.
So for me improving arm and upper body strength helped a lot, that said I do very little arm excercize so they were very weak compared to legs.