If the knuckles don't get bigger because of illness, don't change them deliberately. The phalanges are very fragile. If you correct blindly and use splints, you may be disabled.

If you care about the change of appearance, it is better to cultivate your temperament from an early age.

Read more books, learn to dance when you have time, and eat something beneficial to your health, which is more useful than any cosmetic surgery.