I have a lipoma on the side/back of my knee that is hard and painful. It measures 8.5cm x 7.5 x 2.5. Non encapsulated (Photo)

That is quite a good sized lipoma.  However, most plastic surgeons could remove this under local anesthesia without much difficulty.  Unfortunately many people go to the wrong type of doctor for something like this and they make it more difficult than it needs to be.

Lipomas are benign fatty tumors that occur under the skin and less commonly within the muscle. They are associated with mild discomfort and a lump underneath the skin. It is always best to talk to an expert plastic surgeon to determine whether the lipoma is possibly a cyst or a tumor or hernia. We would have to remove the lipoma to be sure that it is not something else and we usually do this by sending it to a pathologist for evaluation. If a lipoma is painful, then an exam is needed to make sure it is not compressing on a nerve or whether the diagnosis is different. Aftercare for a lipoma includes gentle compression and Plato’s Scar Serum twice daily on the wound.

Best,
Dr. Karamanoukian
Realself100 Surgeon

Thank you for sharing your question and photograph.  In the vast majority of cases lipomatous masses are benign and not cancerous.  Based on its size I would recommend surgical removal for your comfort and ability to wear clothing.