Some symptoms: pain (location varies), smoothness in cadence decreases (perhaps start wobbling in seat), power decreases. Typically it's stated that the "knee angle" should be between 25 - 35°. The landmarks for measuring are the lateral malleolus of the ankle (big bump outside of ankle), the lateral condyle of the knee (big bump on outside of knee), and the greater trochanter ("hip point" or big bump on hip. Note that the hip is not the pelvis but the proximal--closer to the heart--end of the femur). Obviously this produces to line segments roughly following the femur and very roughly the tibia. The "knee angle" is measured as 180°- the angle between those two segments. So if you actually measure the angle between those two segments you should, if you follow the typical advice, get an angle between 145 - 155°. Be careful to not make big changes in saddle height as this can cause injury in some people. It's generally best to change the saddle heigh buy a few millimeters at a time......0-4-ish.