Hi, thanks for your query.
I can understand your problem.-
Bony prominences like knee and elbows are prone to trauma and friction because of which they may develop Post inflammatory hyperpigmentation
For the same you may use a hydroquinoe, tretinoin
, momatosone combination cream twice a day under medical supervision.
You may take a few sessions of TCA spot peels.
Take oral Beta carotene
, Vitamin C
supplements and antioxidants.
The results depend on the depth and extent and duration of pigmentation and vary from person to person.
Hope this helps you.