Pretty much impossible to say without a medical qualification and doing the tests on the players first hand. FWIW it's not a big deal that Tierney was injured when he was signed - most footballers are walking around with one knock or the other at any given time. I remember Henry saying he was in perpetual pain from 2003 to 2007 and you wouldn't have not signed him for your club during that time. The same is true of Suarez, Vincent Kompany etc.
The medics largely manage these injuries - in some instances they are successful e.g. no one comments on what an incredible job they did with recuperating Martinelli post injury and in other instances they aren't. Ultimately if our biggest injury problem is that we have a bunch of injury prone left backs - a position where we have 4 other options - I'll take that any day over Saka or Odegaard being injury prone.
