It is just typical that when Arsenal sign a player they immediately begin to have injury issues. Thomas Partey famously arrived from Atletico Madrid without even a hint of an injury on the horizon and yet they have plagued his career.
Oleksandr Zinchenko however did have injury problems at Manchester City and Arsenal signed him in the knowledge that these existed. To be precise, Zinchenko had 16 separate injury-related issues at Man City from knee surgery to calf strains to simple knocks.
In total, Zinchenko missed 65 matches from the 2018/19 season to the previous campaign. That sounds like a lot... because it is.