It is always interesting and alarming to find a new lump or bump, and it is usually something that should be discussed with your doctor
. Depending on the location of the bump with relation to the rest of your knee, this could be many different things. It could be something as simple as a swollen knee from running too much or doing other physical activities that is causing some local reaction. It could be something related to a trauma or some sort of local infection that has caused some swelling. In the case of infection there would often but not always be other symptoms. Other things are more specific to the knee, such as a Baker's cyst, which can be a small cyst that can sometimes rest near the knee and cause pain for some people. Of course there are other things that can be even more serious and will require further evaluation by a doctor to make sure that you improve as quickly as possible, and so it is important to speak with your doctor about this new finding. Please speak with your doctor.