Hello, * As per my surgical experience, the painful leg with bulging rash on ankle with history of knee surgery indicates possible cellulitis issue via bacterial infection of gram positive bacteria or else. My guidelines at present - keeping the local area clean with antiseptic liquid or soap - calamine lotion application over the rash area - foot elevation over 3 pillows - avoiding prolong leg dependent position - should not use tight shoes - keep ambulatory but not prolong weight bearing - control of blood sugar However, if you can provide a high resolution photograph of the leg showing rash, it would be of immense benefit to co relate on clinical grounds for further discussion and guidelines. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr. Bhagyesh V. Patel