Tripping
Can be caused by loose wires being left around where people could trip over them.

RSI
Caused by repeated actions in a way that puts stress on joints and muscles.

Poor eyesight or "Square Eyes"
Caused by staring at screens too long or when it is in a position unsuited for the users height and angle.

Bad posture
Normally caused by slouching in the chair or using a chair that isn't suitable for the body.