Odile, The good doctors are reminding me of something I always hope people remember when they are writing on the site. Your condition is real, and in this case advanced, and good medical supervision is not only smart but required. To have a doctor you trust and who can follow your process is necessary to get the best advice; even if it's not always what you want to hear.
Likewise the doctors have pointed out the rare use, and often misuse, of cortisone; especially for this largest tendon in your body. In addition to potentionally weakening the tissue you are masking the pain on your feet, which are so consistently used and can be a recipe for disaster. You took five weeks away from your athletics which makes you a perfect patient but I'm guessing you didn't lay around with your feet up and eating Bon Bon's.
I have a man I worked with a few years ago with nearly the same symptoms you are suffering almost down to the detail but within a shorter time frame. His had rapidly deteriorated. however, and was being directed toward surgery to remove the degenerative tissue at the nodule site; I think it's called debulking, atleast that is what his doctor called it. He had already had a cortisone shot but was put on crutches for protection against his tendency to do to much activity with four sons under the age of 15. The next step could have been casting both legs; it has it's own set of problems. The doctor felt certain there was a surgical room with his name on it.
On the one hand he was almost ready to try anything, surgery included, but decided to put 100% into an alternative. And so we trained together for almost a year continuously and then saw each other about every four months to adjust his work over the next year. I called him yesterday to see how he was doing, two years later, and to be sure I had an accurate memory. Basically he is better than even when we stopped training as the healing process takes time and he continued to do the work necessary to perpetuate the progress. He said the most painful aspect of beginning a program of self healing was that it was so little in the beginning and he was feeling so motivated and also that he had to change doctors until he found one that respected his choices and was still willing to take his case and then treat him if a turn around wasn't possible. Sometimes good science is just necessary if a condition has reached an irreversible stage or if the patient can't follow a strict and consistent protocol. You have to go into self-healing with this thought or irresponsible choices can insue.
I am a big champion of natural remedies and have great respect for good medical science.The natural process is slower, as you are assisting the body in it's self-regineration. The natural approach takes more participation on the part of the patient both in terms of attention and time (mb6066 referred to this phenomenon). In a natural approach you have to look at the body as a series of systems that work together in perfect orchestration. If one system is down you can bet there are other systems effecting the process. In natural treatments it is ineffectual to isolate the treatment to the symptom, i.e. the affected area. The medical community can go to the symptom and make a near immediate correction with proper rehabilitation and the outcome can be very positive. But in these cases the rest of the systems should still be evaluated to see why one part of this perfect orchestration failed. This is the way nature and nurture can work together in perfect harmony.
If you catch it in time you may get to see the wonder of our human physiology. If the condition is too advanced, you may see the wonder of medical advancement. Just remember that nurture always incorporates nature; and visa versa. It's the law.