Tendonosis is something which is hard to cure by visiting a doctor. Chances are you'll be given a set of rest/stretch type activities to do. There's not a pill or one-shot treatment that can solve it. (note: tendonosis from what I understand does not in itself make the Achilles tendon more prone to tearing)
I had Achilles tendonosis for a while and found a sort of management place with it. I warm up thoroughly, do post tennis warm-down (walk for about 10 mins) stretches and also off-day stretches often twice a day concentrating on the lower part of the calf. I also do the rolling pin exercise too (can't find the video at the second) which is a Godsend for calf niggles.
Tendonitis however is a whole other story as Ollinger mentions above.
Last edited by Bobby Jr : 04-02-2012 at 10:14 PM.