Mild sprains or other repeated injuries can irritate and tear the thin membrane covering a tendon, causing fluid to leak into a sac that swells and forms a ganglion.
it becomes large it can cause pain, because it can press on your median nerve which can send the pain up the whole of your arm, if it gets this large you will need to have a ganlionectomy which is...
The formation of numerous, closely spaced rills due to the uneven removal of surface soil by streamlets of running water. Also known as rilling; rill wash; rillwork.