I've been playing guitar (both electric and acoustic) pretty seriously for about a year, 2-3 hours a day most days. I couple months ago I developed tendonitis in my fretting arm, which my doctor diagnosed as lateral epicondylitis, i.e. tennis elbow. My doctor predictably recommended laying off guitar for a while, using a compression bandage, icing it, taking ibuprofen, that sort of thing. I didn't see a specialist or physical therapist so the advice was sort of general.
I did more research on my own and found this article which describes a simple exercise that does eccentric loading of the tendon and is supposed to be great for this sort of injury, and it's been helping over the past few weeks. I do that plus daily icing of the tendons, which is also good. After a few weeks of abstinence I've worked up to playing a total of maybe 20 minutes every other day in short sessions (it's really bumming me out and I want to play a little). If anyone has more helpful advice on how I can treat it, I'm open, but I think it's just one of those things where you have to give it a few months to sort itself out.
My main question is this: assume I do all these things and in a few more weeks or a couple months, the pain is gone. How I prevent it from coming back? Do I need to make changes in my warmup/practice or my technique? I've read other questions from guitarists who have had fretting finger or hand pain; mine is related but in a different place.
My teacher, who's been teaching for 30+ years, didn't have anything at all to say about it; he's hardly heard of anyone having this sort of problem. I've talked to others and haven't learned a lot, other than that if you let it heal, you're not doomed to have it come back once you start playing again. I should definitely learn to develop a lighter touch when fretting notes and chords, which is something I've been working on, but other than that while I've heard of other guitarists who have had my condition, I haven't read a lot about what got them there and how they could avoid it.
Here's some additional information on my exact symptoms in case folks find this question because they're looking for info.
The pain is in my forearm, on the top/outside, a few inches below my elbow. When I first started getting it, I thought I might have had pain in the inside of my elbow too, but that wasn't the case -- I just wasn't locating the pain precisely. The pain isn't in the muscle, but the tendons that attach the muscles to the elbow. The pain isn't constant, but only comes on when I move my elbow to the extremes of its range, either bending or straightening, and also if I rotate my forearm outward. I have noticeable pain and greatly decreased grip strength if I extend my arm all the way and grasp something by pinching it between my thumb and other fingers. From what I've read these are all classic symptoms of tennis elbow.
Ironically, I have very little pain while playing, and I don't notice a particular pattern of more or less pain after I play or don't play, even into the next day. The pain isn't that intense; I wouldn't describe it as sharp, but any sort of chronic pain is something to be concerned about and correct; I don't want permanent damage.