I have dark knuckles, knees, elbows and toes. What topical creams can I use to treat it? (photos)

this is genetic most often from your skin type, however, peels and skincare can help lighten t hem. I suggest enlighten or cosmelan peels now with vivatia foam, phytoplus, cosmelan2 and retinol regularly.  along with sun protection.
Hyperpigmentation from any type needs a combination approach of peels like cosmelan,  lasers like clear and brilliant and aerolase or laser genesis, radiofrequency like venus viva, and constant skin care and sun protection.  Bimontly facials with silk peel dermalinfusion is essential to hydrate, exfoliate and infuse vitamins and antioxidants into the skin.  If you have acne you can do additional treatments and peels to get more improvement.  I suggest a formal consultation with an expert in lasers and peels. Best, Dr. Emer.

Our treatments use combination therapy to improve the epidermis and dermis for most deep scars. The options available for acne scars depend on the character of your scars, in terms of topography and contour. We see atrophic and hypertrophic acne scars, as well as scars that have hypo and hyperpigmentation. We begin each scar evaluation with an assessment of scar quality and subtype. Our main concern is rebuilding collagen and that is why we use a HIDEF protocol that includes combination therapy. Morpheus 8, scar subcision, fibrous release, fractional laser, CO2 laser, Thulium laser, PDL Vbeam laser, and fractional resurfacing can be used in addition to TCA Cross and chemical peels to further improve skin. Patients should start Melarase AM and Melarase PM for active hyperpigmentation. Always begin with a consultation to decide whether early subcision should be started.

Best,
Dr. Karamanoukian
Realself100 Surgeon

Try using hydroqionone.  It is a topical lightening agent that you would most likely benefit from.  Good Luck!