The general topic of this contribution is the knowledge of science teachers and the evolutions of this knowledge, involved in their lesson preparations and implementation in class. We study the case of two teachers of physics and chemistry at middle school (9th grade) in teaching mechanics and two teachers at elementary school (in 5th grade and 4th grade) in teaching electricity. Our theoretical approach refers to professional didactic to analyze developments in professional knowledge and to the concept of PCK from Shulman (1986). The data we collect are interviews with the teachers and classroom videos. The researcher then organizes a stimulated recall with pairs of teachers, focusing on critical incidents (corresponding to gaps between the preparation and the implementation). Analyzing these data, we show that there is a relationship between knowledge and retroactive control that allows the teacher to adjust his/her preparation. When there are deficits of PCK, the types of knowledge used by teachers are different in nature, depending on whether it happens during the preparation of a new lesson or in action of classroom.