Our nine year old bruises easily from simple knocks on the desk. His left arm has a few small round bruises. He bangs it on the table and knocks it on the door knob. Things like that. Only this left arm most of the time. We rarely see them anywhere else. He bounces and thrashes around our claustrophobic house. Would you worry? I don't know if it's considered "easy" bruising to get it from knocking his arm rather than big falls, etc. Thank you xx