For whatever reason, it seems Dave Tendlar did not like to draw Popeye's knee caps. Many drawings do have them, but generally speaking, most of them are missing that part of the anatomy. Unlike his fellow animators, Tendlar would streamline the shapes of the legs instead of drawing them like the model in segmented sections. The following clip of his animation from The Man on the Flying Trapeze is a great example of this particular drawing earmark.
Some other examples from posted clips -