Hello, You are having an itchy bulge behind the knee. It s presently not hurting. Dark spots in the veins appear to be making up the bulge. Your symptom may be indicative of abscess, boils, hematoma, sprains and strains, tumors, malignant tumors, deep vein thrombosis, baker s cyst, synovial sarcoma, etc. Cyst, is usually the result of a problem with your knee joint, such as arthritis or a cartilage tear. Baker s cyst is a fluid-filled cyst that causes a bulge and a feeling of tightness behind your knee. It may not pain at the initial development but with the growth of the cyst the pain can get worse when you fully flex or extend your knee or when you re active. Synovial sarcoma is a malignant growth that forms a lump behind the knee. It may require prompt treatment. You are suggested to get clinically examined by a GP, get your knee examined, get all required tests (X-ray MRI, Ultrasound), blood workouts, urinalysis, etc., done. You will be accordingly treated with oral medicines, diet restrictions, cyst aspiration or drainage and surgery (if needed). Avoid activities that strain your leg, rest your leg whenever possible, apply ice to your knee. Elevating your knee while you are resting and compression wraps are helpful. Avoid strenuous exercises. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician