I have to agree with Frailty here, for the most part.
Whilst this may not be a very popular opinion, I can only surmise that it was an attempt to milk a penalty gone wrong.
I do believe it was a penalty because McLean did place his hands betwenn McKinnon's legs. But he was barely, if it all, lifted above the horizontal.
He was on course to be tackled almost horizontal to the ground until a last split second decision to inexplicably tuck his head in. I could understand it if he was being driven head first into the ground but the footage clearly shows he wasn't.
Perhaps he was somewhat disorientated.
I do of course wish him a full recovery as much as the next person, but that doesn't mean I have to be hysterical because of the outcome of the incident.