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Postural control in rheumatoid arthritis patients scheduled for total knee arthroplasty.

OBJECTIVE
To investigate the use of compensatory visual and attentional control strategies for standing balance in patients with rheumatoid arthritis (RA) with severe knee joint impairment.


DESIGN
Experimental 2-group design.


SETTING
Specialized clinic for orthopedics, rheumatology, and rehabilitation in The Netherlands.


PARTICIPANTS
Eighteen patients without comorbidity (age range, 65 +/- 7.7 yr; 16 women, 2 men) from a consecutive sample of patients with RA scheduled for total knee arthroplasty; 23 controls of the same age group also were tested (13 women, 10 men).


MAIN OUTCOME MEASURES
By means of a dual-plate force platform, the velocity of center of pressure (COP) fluctuations were analyzed in the anteroposterior and lateral sway directions during quiet standing with eyes open, eyes closed, and while performing a secondary attention-demanding arithmetic task.


RESULTS
Patients showed an average 80% greater COP velocity in both directions of sway compared with controls. In addition, stability deteriorated substantially more in patients than controls when deprived of visual information, which was associated with the degree of knee destruction. The effect of the arithmetic task was small and similar in patients and controls.


CONCLUSION
RA patients with severe knee joint impairment can have a substantial basic postural instability; their relatively high reliance on visual information suggests impaired sensory feedback from the lower limbs. Current research is aimed at determining whether these postural deficits can be improved by total knee replacement.