There are two sets of joints that see much more mobility than others, that are not your hands and feet. Your knees and elbows see much more motion throughout most given days than other parts of your body. With every step you take, your knees go through ever continuing stress. Knee pain is common in those who do athletics, and runners especially. It is very common for those runners who have knee pain to be running with poor shoes, or on inflexible surfaces, like concrete or brick roads. These are just a couple of different causes of knee pain.
Knee pain can be difficult to treat because they are essential to a person’s mobility and restricting the motion of a person’s knee, can without cause, damage it further. Obviously, things like knee surgery, which athletes and runners often need are unavoidable. Partly this is because of the amount of work those people put through their knees causes the joints and ligaments in them to wear and even tear on occasion. Even if you are not an athlete, you should make sure to only wear shoes that are well cushioned and supportive, as well as exercising on softer, more flexible surfaces.