Have A Reddish Purple Flat Rash Around Knees And Some

Have a reddish purple flat rash around knees and some on upper/lower legs, no raised bumps, no itching, no discomfort form it now. FYI have knee replacements in both joints.

Swam in a chlorinat pool over the week-end but have done that oover the summer.

Thank you in advance for your assistance.