a2 - test (v5)The True Cause of Knee Pain and Cartilage Wear: Worn out cartilage in the knee is one of the most common causes of persistent pain and limited mobility. It begins when the cartilagethe natural shock absorber between the bonesis slowly broken down. Once it's gone, the bones rub directly against each other. This leads to pain, stiffness, and swelling. Even simple activities like walking or climbing stairs can then become painful. And what's the main