That video doesn't show his legs
I don't think it's old sickly Biden.
>>21276526 (PB)
His legs are shown in the video from this post. You can see he walks with his knees. The bend and extend like a health/youthful person would walk.
Compare that video to how he walks in this you tube video from 3 months ago.(starting at 22s).
His knees are mostly locked at an angle as he walks his old man walk/shuffle.