Hi,
I recently started learning guitar using Justin’s website - it’s great! However, I came down with sudden tendon irritation in the bottom knuckle of my left index finger after just a few weeks of playing - pain, swelling, etc. I’m kind of surprised this happened, because I only played for up to 10 minutes at a time (new student, busy parent, etc).
My doctor gave me a steroid injection and after a few weeks rest, I’m finally feeling much better. I’d like to gently and carefully try guitar again, so I’m looking for tips on how to avoid tendon problems in future.
Advice welcome please!
Thanks!
Short answer is I don’t know I’m not a medical expert. It seems like an unusual injury, maybe it was aggravated by playing guitar but I don’t think such a tendon issue is likely to have been directly caused by playing.
I’ve posted this before when people have asked similar questions. I found the exercises helped me. It’s not specifically about fingers but just for general health of the elbow, muscles, wrist etc.
Are you using the “grip of death”? Like you’re choking a Klingon? 
Seriously, perhaps your grip is too strong.
Also not a medical expert, but have been having similar issues lately. Stretching exercises before playing have helped somewhat - you can find lots of videos for that on YouTube.
Also suggest you search this forum for “arthritis” - not sure if that’s you’re issue, but I recently did that search (it is part of my issue) and the posts/responses/comments have tons of great info about all kinds of pain and injury issues related to playing the guitar as well as a lot of resources for managing or fixing the issues.
Best of luck - I hope this doesn’t get in the way of your playing