Evaluation of knees of tetraplegic patients who have been walking for several months with the aid of a system that involves neuromuscular stimulation, treadmill and a harness support device. To investigate if the training program could cause knee injury to tetraplegic patients. Hospital das Clinicas - UNICAMP. Campinas-SP, Brazil. Nine patients were evaluated. Clinical exam and magnetic resonance images (MRIs) were used for evaluation. MRIs were taken before and after the training program, in a 6-month interval for each patient. There were two sessions of training every week. Each session lasted 20 min. No severe clinical abnormality was observed in any patient. Mild knee injury was observed in four of nine patients studied. Tetraplegic patients undergoing treadmill gait training deserve a close follow-up to prevent knee injury.46124-8