To illustrate both physical and psychosocial effects of moderate gonarthrosis, clinical examination of patients has been supplemented with a questionnaire SIP (Sickness Impact Profile), to describe the functional health status. Sixty patients, 35 women and 25 men, mean age 63 years, with moderate medial osteoarthrosis of the knee and no symptoms from other joints, were included in the study. The mean BOA score and the self-selected walking speed were decreased in these patients compared to normal individuals. All patients graded pain during walking. The SIP revealed both physical and psychosocial changes in these patients with moderate gonarthrosis. Patients considered that their knee osteoarthrosis had great influence physically on ambulation, during recreation and pasttimes, during sleep and rest, and psychosocially on emotional behaviour. Significant correlations (p less than 0.01) were found between pain during walking and the psychosocial questions in the SIP, between the BOA score and questions in the SIP concerning the physical performance, and between self-selected walking speed and the physical questions. It is concluded that the SIP appears to be a measure with sufficient sensitivity to detect physical and psychosocial changes in patients with moderate osteoarthrosis of the knee. In clinical practice determination of self-selected walking speed and pain during walking will appropriately reflect general function.