RESUMO
BACKGROUND: Individuals with systemic sclerosis have muscle functions with varying degrees of muscle weakness and atrophy, which in turn can have a negative impact on functional and health-related quality of life. This study aimed to evaluate peripheral muscle performance using isokinetic dynamometry of the knee in women with systemic sclerosis and to correlate peripheral muscle dysfunction with disability levels and general fatigue. METHODS: Twenty-six women with systemic sclerosis and a matched control group with an equal number of women underwent knee isokinetic dynamometry at angular speeds of 75°/s and 240°/s, isometric handgrip strength, the Health Assessment Questionnaire Disability Index, the Functional Assessment of Chronic Illness Therapy-Fatigue scale, and the Fatigue Impact Scale. FINDINGS: Women with systemic sclerosis showed significant reductions in almost all isokinetic parameters for the two angular velocities tested compared with the controls. An agonist/antagonist ratio with values <40% was observed in approximately one-third of the patients. These patients had lower isometric handgrip strength. These patients also performed worse on the two general fatigue scales evaluated. Significant correlations were observed between the isokinetic parameters and the measured isometric handgrip strength, and the Health Assessment Questionnaire Disability Index. INTERPRETATION: Systemic sclerosis patients have reduced strength and endurance as well as a muscle imbalance between the quadriceps and hamstrings. In these patients, lower muscle dysfunction of the knee joint is associated with lower handgrip strength and physical incapacity.