How do you manage pigmentation on your underarms, elbows, and knees?

I'm worried because my armpits, elbows, and knees are particularly dark.
My underarms look darker than other areas, perhaps because of hair removal or skin irritation, and my elbows and knees definitely look darker, perhaps due to a lot of friction.

I've tried whitening creams and body products, but I haven't seen any noticeable improvement, so I'm looking into treatments as well.
I am wondering if lasers like toning are suitable for pigmentation in this area, or if I need to receive a different treatment.

My underarms, in particular, tend to be sensitive, so I am worried that the pigmentation might become darker after the procedure. I am also curious to know to what extent the procedure can improve old pigmentation, such as on the elbows or knees.

If anyone has received treatment for similar hyperpigmentation, please let me know what treatment you received and how many sessions were needed to see results!