The crooked fingers seen in the picture are very likely because of osteoarthritis of the joints. Due to severe cartilage wear and destruction, the joints become progressively deformed and bent.
Unfortunately, this is an irreversible process.
If there is a lot of pain in the joints with swelling, treatments are targeted to reduce inflammation with splinting and rest, warm packs and oral medication. The only solution to correct the deformities in the joints is surgery. The operation is done to resect the damaged joint and fuse either ends of the bones together in straight alignment using metal wires or plate and screws. This not only corrects the deformity, but it will also eliminate pain from the worn-out joints. However, the result will be a fused joint with absolutely no movement at the joint. Therefore, one would be sacrificing joint motion for deformity correction and elimination of pain should one decide to undergo surgery.