<s>[INST] Hi my name is Kayhan and I have a bump on the inside of my left knee. It looks the size of a golf ball. It hurts when I walk, run or apply pressure on my left leg. It is very bony and causes strong pains that sometimes make me cry because it is really bad [/INST] Hi, dear. I have gone through your question. I can understand your concern. You may have some bony tumor or other lesion.  You should go for x-ray knee to know exact location and origin of tumor.  Unneeded go for biopsy. 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>