Hi, dear I have gone through your question. I can understand your concern. You may have some soft tissue tumor like lipoma, neurofibroma or dermatofibroma. You have history of trauma and surgery on ankle. But your ankle lesion has nothing to do with knee swelling. You should go for examination. If needed go for fine needle aspiration cytology or biopsy of that lump. It will give you exact diagnosis. Then you should take treatment accordingly. Hope I have answered your question, if you have doubt then I will be happy to answer. Thanks for using health care magic. Wish you a very good health.