Knee pain, swelling, difficulty going up and down stairs, and inability to walk are likely to have cartilage wear, but often there is a bone support structure is the first to go wrong, and the root cause is osteoporosis. The relationship between cartilage and bone is like a layer of PVC plate on the ground, the foundation is solid, PVC plate running cars are no problem; if the foundation is hollow, put a tire can collapse the plate, lose shock absorption, smooth performance. Without cartilage plate, it is inevitable that the bone and bone friction. Pain, bone flab due to this.