Okay, so I have hEDS, also known as Hypermobility Ehlers-Danlos Syndrome. I do not produce the right kind of collagen, and therefore my ligaments and tendons are more likely to be injured. I have a heavy duty knee brace from the Doctor, but I can't wear it under clothes and the seams of my jeans press into my leg when wearing it. Copper helps reduce inflammation and tightens tendons and ligaments. These babies are amazing for my knees! I wear a size 16 in jeans and require the XL. I would rather have a dimple in my thigh from the upper bands then the painful impression of my jeans. But I have to say that these braces keep me going throughout the day. It is truly amazing that they help so much since they look so flimsy!