From The Art and Popular Culture Encyclopedia
Locomotor ataxia is the inability to precisely control one's own bodily movements. Persons afflicted with this disease may appear to walk like defective robots or otherwise move like malfunctioning machinery; that is to say, in a herky-jerky, up-and-down kind of rhythmical but non-fluid manner. It is often a symptom of either advanced Syphilis or Tabes dorsalis.
It is caused by degeneration of the posterior (dorsal) white column of the spinal cord. The patient doesn't know where his arms and legs are unless he looks, but he can feel and locate a hot object placed against his foot.