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.
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:RApatients 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.