Once the leg has straightened, it must stay straightened until the leg passes the vertical position. Actually, keeping the leg straightened beyond the vertical position is fine and even desirable. Observe the leg position in the image on the right: the walker not only follows the definition, she also keeps her leg straightened after passing the vertical position. This leads to increased forward drive and removes any doubt from the judge that your leg is straightened long enough.
While violations involving loss of contact tend to occur more often at short races, bent-knee calls frequent competition at longer distances. The longer a race lasts, the less lifting occurs; conversely, creeping tends to increase. Inexperienced race walkers typically struggle more with straightening the knee, whereas elite walkers face greater problems with lifting. While strong competitors try to avoid either violation, they usually walk as close to the periphery of the definition of race walking as possible.