I am trying to measure the angle of my knee at the 12, 3, 6, and 9 o'clock crank arm positions by laying out lines on photographs take from the side. It seems to me that the line for the lower leg should run up the shin because the bone is right there. However, where should I put the line for the upper leg? The top and bottom of the thigh seem inappropriate because of the contours of the big thigh muscles, and it is not easy for those ignorant of human anatomy to guess exactly where the thighbone is. None of the cycling books I have read give instructions on exactly how to measure the angles they refer to. Any suggestions?