When we experience pain, two areas of the brain receive the pain message. The front of the brain is the processing area which thinks about the pain, what its cause may be, why it is persisting and what can be done about it. The subconscious part of the brain also receives a pain message and will then send a message back to the muscle. If these pain messages are sent frequently to the subconscious, for example by putting weight through a painful hip, then voluntary control of our muscles becomes impaired. Effectively we consciously want to move, but out subconscious does not want to, to avoid provoking more pain, hence the muscles gets a ‘mixed message’ and the shakes then result.