Locomotor ataxia is the inability to precisely control one's own bodily movements. Persons afflicted with this disease may walk in a jerky, non-fluid manner. They will not know where their arms and legs are without looking, but can, for instance, feel and locate a hot object placed against their feet. It is often a symptom of tabes dorsalis, which is a key finding in tertiary syphilis.
It is caused by degeneration of the posterior (dorsal) white column of the spinal cord.
The chilling effects of this condition and its connection to venereal disease are dramatized in the story "Love O' Women" by Rudyard Kipling.
References
Locomotor ataxia Wikipedia(Text) CC BY-SA