While I prefer shooting from both knees, it's not always possible for me. Thirty years ago, a horse I was trying to rope took exception, and kicked me in my right kneecap, shattering it all over the place. That smarted a bit. The surgeon did an outstanding job, as I've only started having mild problems with it in the last few years. But, I could never put much weight on it directly, due to whatever he used to re-attach things. I can feel these lumps under the skin, and they tend to be touchy. A pad usually makes it tolerable, however.
Murray