Peroneal tendonitis

About 3 years back I ran a marathon in some really shoddy shoes and my right ankle has never recovered. I can still run but if I try to do any range of motion exercises, like flossing and calf raises (inc KOT), my ankle keeps popping and starts getting sore. Have been to a doctor/specialist and have had both an MRI and ultrasound. The result was that the peroneal tendon is split and there was not really a definitive answer other than ‘if you can still run, leave it until it gets worse’ or ‘you can undergo surgery to deepen the groove the tendon sits in’. Don’t really want to go down the surgery route, anyone had any luck with this condition?