This is Dr. David
this dark brown color skin on your shin and calf and feet can be old blood from bruising from the total left knee replacement surgery.
or it could be due to venous status changes from poor circulation in your leg from your surgery.
you should ask for a doppler ultrasound scan of your leg to check for proper blood flow arterial and venous
old blood under the skin can take months and months to slowly be absorbed into your body.
let me know if you have questions.
cutting down and stopping the 3 pints a week will help your knee recover better and help your circulation in your lower leg.
yes, cold blood can still make your skin look dark.
I would work on quitting alcohol before you have your next knee surgery.
thanks for the positive feedback.