I get bruise black marks on my legs below knee caps..how to remove these black scar marks there legs?

sir.in my early age i used accidentally 'erythromycin caps for allergy but late on i used to get black marks on my legs after after wounds like cricket balls or scooter kickers etc..even a small scratch will leave a dark mark..onlyon my frontal legs ie below knees and above.ankles.pl advise me for treatment..pysoriasis is ruled out..