Before exercise or any activity you should do Warm up and after activity you've to calm and relax your body.
If you're not doing above things then the possibility of of injuries gone 10 time increase.

Because of warm up you'll be flexible and much active and after relaxation your muscles goes calm and the chances of injuries gone to be decrease.
After Injury Always Remember These Following Points:-

1) Fomentation-

Do fomentation after injury by Ice, by this the blood circulation is going much slower and the injured area didn't swell. Don't do massage with hot oil otherwise the blood circulation is going to be fast and the swelling of injured are is also going to b increase.

2) Rest-

Don't do unwanted activities and movements after injury, take proper rest.

3) Crepe bandage-

Use crepe bandage to the patient after injury so the bone is not moving from its place.

Mostly 40% of cases are visible in sports ground, 20-22% cases are just because of providing wrong training by the trainer and 10% of injuries happens because players don't have the proper knowledge regarding Rules & Regulations.

Only a sport person is not going to be injured during playing games or participating in any activity, it can happen with anyone if he/she is doing exercises without warm up.