I currently have tennis elbow (lateral epicondilytis). This is the 4 fourth time it's flared up.
Caused by overuse - previously got it from playing too much guitar, too much kitesurfing, and this time to much supping+surfing. Last summer I pre-trained my arms before summer, and got through without pain, but somehow it came back.

I used every technique to cure it each time, and each one worked differently:
Different combinations of rest, massage, acupuncture & cortisone. My research say no diffinitive fixes. It's a bugger of an injury.
Once, a week of solid rest fixed it - i.e. bandaged the arm up like it was broken & didn't move it/use it. It's hard to treat a hurty elbow seriously, whereas a broken arm, nobody questions putting it in a cast until it's healed.
Other times, it's lasted 12 weeks. Acupuncture halved the pain. Once, it just wouldn't heal, so went the coritsone and that got it over the line, but not a fan of cortisone.
This time, trying rest... acupuncture next week ... shall see how it goes...