Once you have a serious ankle injury it leaves you susceptible to turning it repeatedly. You can run all day on the track or road, but on a grass surface it is spongy and puts extra strain on the ankle weakness.

I know this through first hand experience. When I was 16 a lad I knew deliberately stamped on my ankle while I was on the ground. Did not break it but I struggled to walk for 2 months. I never played again. Even to this day on occasions when I mow the lawn my ankle goes again and I struggle to walk for at least a week.