This is a good self audit test that reveals poor knee control.
Step 1) stand barefoot on a staircase step (about 6″)
Step 2) step forward with one foot, tap your heel the the step below, and return.
Step 3) observe the path of the knee upon which you are standing.
If you cannot keep the feet pointing forward and the heel of the stance foot flat to the step, then you need to check the ankle you are standning on for mobility.