[Coccygodynia: value of dynamic lateral x-ray films in sitting position].

In coccygodynia, pain is most severe in the sitting position. This prompted a study comparing lateral roentgenograms of the coccyx taken with the patient lying on the side. In this prospective study, eight of 30 patients had posterior subdislocation of the coccyx which caused pain and was visible only on the films taken in the sitting position.