Source: Rheumatology  |  Posted 9 years ago

Secondary plastic changes in the central nervous system generate and maintain the perceived joint stiffness (PJS) characteristic of rheumatoid arthritis, say researchers in the United Kingdom.

This is "causally related to the initial peripheral rheumatoid disease process," according to R.C. Haigh and colleagues at the Royal National Hospital for Rheumatic Diseases and the Department of Medical Sciences, University of Bath.

In this study, rheumatoid arthritis (RA) patients with phantom limb pain following amputation clearly showed how much the subjective experience of perceived stiffness was dissociated from the assumed original peripheral source. While PJS is a known defining symptom of RA, its nature and cause is unclear.

To test whether this subjective feeling of stiffness in a limb following amputation is sustained by changes in the CNS, the authors systematically checked patients with a phantom limb (PL). Three subjects, with characteristic RA stiffness prior to lower limb amputation, were investigated to define the nature, stiffness and pattern of pain in their PL and intact limb.

Visual analogue scales were used to measure pain and stiffness severity in both limbs.

A standard physical examination was also carried out and recordings were made of the duration and timing of stiffness for each limb.

Similar patterns of perceived RA stiffness were found for the intact limb and the PL in all 3 subjects. In terms of quality, frequency, diurnal variation, location and distribution they all reported stiffness in their PL which mirrored that of physical RA joint symptoms.

This similarity was also seen in their response to the medication of non-steroidal anti-inflammatory drug, corticosteroid, opiate and disease-modifying anti-rheumatic drug.

Stiffness was only relieved in the limb being exercised through unilateral exercise or attempted exercise.