Tightness behind the knee

Hi, when I do most of the hamstring/pike stretches, I feel it most in the back of my knee rather than in the hamstring. If I bend my knees slightly then I feel it in the hamstring. Coach Sommer in the videos makes a point to tell us to keep our knees locked out and I have seen that repeated by other coaches on the forum.

what is likely to be causing this tightness? Should I carry on with locked knees and in time the area being worked will shift?

thank you, James

Straight knees pain it is associated with tight calves, if you are searching for specific hamstring then you can work separately on some bent leg variations prior to the straight legs variation.