Article is dealing with an incerease of patelofemoral force as a result of reaction of the knee brace on the patella. It tries to respond to the question how much the reaction of knee brace increases the stress in patello-femoral joint during ordinary locomotional movements. It also deals with the essence of patellar opening in the knee brace which is supposed to decrease the force on patella. Four serially produced braces determinated for involvement of patelofemoral joint compactness available on our market were compared. Magnitude of the reaction between brace and patela was scanned by a sensor from conducting elastical material in four positions during walking in range from 0 to 50 degrees. Realization of the experiment brought these results: – with growing flexion of the knee joint increases the force on patella; – measurement did not certify big differences of the reaction in relation to material or construction of the brace; – forces arisen by an aplication of the knee brace reacting like additional load with patello-femoral joint are negligible in comparison with the force of patello-femoral joint. Therefore it is not necessary to require the patellar opening on judged type of braces.

        Key words: patell-ofemoral joint, patello-femoral force, knee brace