Hi,
Welcome to icliniq.com.
I understand your concern.
As per the image and information provided, it is PIH or post-inflammatory hyperpigmentation, which are dark spots appearing after any inflammatory response like allergies, pimples, wounds, insect bite reactions, etc. PIH usually appears after the wound is healed and stays for years which may fade with time or become darker in case of frequent sun exposures. Although harmless, they can be cosmetically bothersome.
My advice:
1. Ecglow G cream (glutathione, vitamin C, vitamin E), the combinations in the above-mentioned cream, are available online. If not, you may buy any brand with the above content in them to be applied on the knees and the dark spots at night in a very thin layer in a very small quantity till the darkness reduces in appearance. It may take months to show changes as it is a slow process.
2. Tablet Ascorbic acid 500 mg once daily to be taken after dinner for two months.
3. Capsule Evion 400 mg (vitamin E capsules) once daily after breakfast for two months.
4. Evion one capsule to be broken up and mixed with aloe vera gel to be applied in the morning on the affected areas (knees and dark spots on legs), keep it for two hours, and wash off. This procedure can be done at home. The content, when mixed with aloe vera gel and applied for a few hours, will help with the reduction of the intensity of the darkness on the spots and knees.
5. Glutathione soap for cleaning the knees and dark spots only. Apply the soap after lathering. Please keep it for 3 minutes and wash it off. Do not apply on normal skin. The rest of the body's skin may be washed with a regular soap.
6. Laser therapy and chemical peels are other procedures that may be done to reduce the intensity of the darkness. But, again, kindly consult a dermatologist for more details and for undergoing the procedures. Any treatment done for skin lightening would take time to show results, so consistency is key.