I'm a 35 year old male. I weigh about 255 lbs and my height is about 5'9 1/2". About 4 or 5 years ago I started getting severe leg pain. It hurts to bend and to get up. I can hardly straighten my leg. I also get pain throughout my entire leg and behind my knee. Then about a year ago this hard painful lump appeared on the left side of my left knee. The lump is hard and is tender to the touch. My leg sometimes gives out on me or I have a severe limp to my walk. I've had x-rays done on my leg in previous years. No one has been able to tell me what's causing this pain. The pain has been almost unbearable during this past week. Painful to the point where I can't walk or stand up without almost coming to tears. I'd greatly appreciate some answers. Thank you.