Players are coming back quicker and quicker from ACL reconstruction, where you can be cleared in as little as 6 months to resume athletic activities. My experience from a coaching perspective, its a little bit deceiving because while they are cleared most players don't get the full muscular strength return until well after a year. Players lose a ton of muscle mass in those 6-12 months and those losses are rarely standard.
Traditionally, the habit it is to add bulk (which normally adds slow twitch muscles) to protect the knee. Some athletes lose explosive ability because it is really hard to retrain muscles and rewire them after everything they've done for two calendar years is slow-slow-slow. A lot of rehab programs are now focusing on explosion training rehabs (which used to be frowned upon because perceived stress) and developing fast twitch and acceleration/deceleration these days to help players recover explosive abilities quicker. There is a bit more risk, but in the same way with UCL tears (Tommy John), but players can exit the rehab now potentially in a better muscular position than when they entered it.
Knight hasn't had bounce and the type of explosion we saw prior to the injury. There are a lot reasons or potential reasons as to why that has occurred, and the severity of the injury and muscular damage done is an entirely plausible answer to his slower return. I'm not saying that anyone screwed up his rehab, but the recovery to a serious joint/muscle injury is rarely linear. The expectations for Marcus might be in one place, the results in another and his ability somewhere in the middle at this point. I think he'll get better and more explosive as he gets more time, and while I'd advise patience, I'm not Marcus, the coaching staff. Just a pedestrian ex FB coach who provides overly wordy responses on a fan message board.