It's way, way, way, effing WAY too soon for him to be up and around.
Really, the way I feel about this story line should make me grade every episode as an "F." There's absolutely no point to this story line as it is unless it was a way to make Lindsay and Anna Belknap more tolerable. But they could have done that in a less drastic way that didn't waste Carmine Giovinazzo's talent. Plus, "more tolerable" doesn't equal "good" or "I've changed my mind completely about the character after four episodes," so even if that was their intention for the story line they still failed.
To go from having a 10% chance of ever walking again to walking with a cane in the span of five episodes is ridiculous. It may not have been ridiculous if the story line was the main focus of the show so that we could really get a feel for Danny's struggles and victories; but with the too brief glimpses we got as a side story it just feels like it was a waste of screen time. It also didn't help anything that they completely effed up the timeline by making the Danny story line jump months ahead and Haylen's story line jump only a couple of weeks ahead in the same amount of episodes. There wasn't enough shown for me as a viewer to get invested and not enough to really make me believe Carmine's performances even though I thought he's knocked them all out of the park.
I just really don't know what TPTB was trying to achieve, but whatever it was they failed big time. I mean fail of epic perportions. I would expect much better from a franchise that has Doc Robbins and had Dr. Giles as characters.