The investigators hypothesized that an eight-week collective group exercise program would improve pain, quality of life and functional capacity in patients with knee osteoarthritis (KOA) compared with those receiving no exercise intervention.

Inclusion Criteria:

• symptomatic and moderate to severe medical diagnostic of KOA.
• Subjects with normal cognitive functions and no restriction to perform physical activities were recruited from the hospital's KOA database and eligible to participate if they had presented: Lequesne questionnaire criteria (5 - 13.5), knee pain score between 3 and 7 (on a 0 -10 Visual Analogue Scale), stable doses of non-steroidal anti-inflammatory drugs (NSAIDs) and no regular physical exercise or use of canes in the months prior to the study.

Exclusion Criteria:

• Symptomatic heart disease; symptomatic disease of the lower limbs (other than KOA); symptomatic lung disease; severe systemic disease; severe psychiatric illness; regular physical exercise (three or more times per week for at least 3 months); drug injection in the knee in the previous 3 months; physiotherapy on the lower limbs in the previous 3 months and absence in two consecutive training sessions or three nonconsecutive sessions