Our aim is to automatically detect cow's leg problems. The first system is a four-balance system, where each of the legs is weighed when a cow is in a milking robot. Its functionality is limited to milking robot and complications in interpreting results occur, since often not all of the legs are properly in each balance or the cow is leaning the robot. Therefore, we introduce a new system. It is a mat made of electromechanical film, Emfit, which can detect only dynamic forces. Its benefit is that its use is not limited to milking robot, but it can be set up in any corridor along which the cows walk. Preliminary tests with walking cows indicate that it has potentiality to separate lame cows from healthy cows by different force-time behaviour.