<s>[INST] Hey, I m a 26 year old relatively healthy female. Earlier today while putting on my pants I noticed a rather large lump located about 2 inches below my right knee on the backside. It seems to have just appeared overnight. It has even grown over the last 10 hours. Please help. Thanks! [/INST] Hi, dairy have gone through your question. I can understand your concern. You may have some cystic lesion, hematoma formation, edema or some tumor pathology.  You should go for examination. If needed go for ultrasound study or fine needle aspiration cytology. 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 Chat Doctor. Wish you a very good health. </s>