Question 135: Tennis elbow

I'm a 40 year old, high purple belt. I have only been training for 4 months, but I take it very seriously, and attend class three times a week. I have developed a bad case of Tennis Elbow, a severe pain on the outside of the elbow, high on the forearm. The only way to treat Tennis Elbow is to rest it for 6-8 weeks but there is no way I can stop training for that long.

When doing punching drills, (with no targets) or doing forms, my passion gets the best of me and I give it all I have, in terms of intensity. My theory is that I'm over extending my arms while punching hard or fast. When I throw a punch, I extend until my arm stops. In other words, I lock my arm at the end of the punch. When I'm punching hard, I think that the momentum is hyper extending my elbow just a bit. If I try to leave a slight bend in my arm and not extend all the way, I punch slower and with less power.

Have you heard or seen this before? Am I punching incorrectly? Should I leave a slight bend in my arm when throwing a punch?