What does a jammed knee feel like?

Answer 1

Imagine your leg was a flat inner tube. Imagine pumping air into that inner tube which slowly begins to fill up. With just enough air you can bend the tube in half with relative ease. Now Consider the joint where the inner tube bends as your knee joint - pumping too much air into the inner tube makes it difficult to bend the tube in half. In other words a sprained knee feels like your knee joint is filled with too much air making it difficult to achieve a full range of motion.