I developed a posterior impingement problem after a 4 ligament ankle sprain. After PT initially and plateauing I was referred to a surgeon and then PT again and then a Sports Dr and then another surgeon who finally removed an os trigonum and another jagged bit of bone from my ankle joint. I found cortisone didn't make a difference prior to the surgery (I had 2 injections before he sent me to a surgeon again). Post-op things are better and I had another steroid injection when things flared up which worked well to control pain.

I found swimming really sore because the motion constantly put my ankle in that PF and impingement position and it was much worse with fins. I had some calf shortening after the injury too and lotsa calf stretches helped to restore my biomechanics and gap the posterior part of the joint a bit.

I would imagine that if he wants to continue to train and compete at elite level Rx is going to have to be symptom management and maybe semi-regular steroid injections - an opinion from a sports physician about surgical management could be useful too.