<s>[INST] Hi I have a large lump on my right thigh just above the knee and slightly to the left it is 2 inches across. It came up suddenly overnight and was quite painfull the pain has since subsided but lump remains my doctor has no idea what it is and I am waiting on ultrasound scan. Could you give me an idea of what it might be as I am very confused [/INST] Welcome to Chat Doctor. 1. History suggest most possible cause could be - ganglion which arises from the joint space.2. Could be from tendon, synovial, nerve - most often after a trauma. Its pain less around the joint space. Other possibilities vascular pathology.3.However ultrasound will help to find out the nature of the lump (solid, cystic, mixed) and source of the lesion and where all it is extending.4. If anything related to joint MRI is excellent tool to evaluate the pathology.5. So please wait for your scan - things should be clear after that. Good luck. Hope I have answered your query.Anything to ask do not hesitate. Thank you. </s>