Various factors are responsible for this. Few are unavoidable and some can be modified.

• Repeated use of certain type of shoe like high heel, small and narrow toe box shoe can forced the toes to bend and remained curled up for long that they may not be able to straight on bare foot.
• Osteoarthritis and trauma

Toe become painful due to formation of corn and calluses at dorsal aspect of deformity and toe tip. Sometime wearing foot wear become painful.

One should visit a specialist when the toes become painful due to corn/calluses. Sometimes anxious person visit a clinic for cosmetic purpose. 

Deformity is diagnosed by clinical examination. Your doctor will examine your foot to find other associated deformity and any predisposing factor.

Selfcare and prevention: 

• If your toes are still flexible, performing regular exercises of foot intrinsic muscle may help alleviate your symptoms or prevent them from getting worse
• Moving toes passively toward their natural position can help improving the deformity.
• Wearing shoes with soft, roomy toe boxes and avoid tight shoes and high-heels
• Using friction protecting silicone gel cap, sheet and spreader also helps in preventing painful corn formation.

Based on your symptoms your doctor may advice you

• A special insole or metatarsal pad that can redistribute your weight and relieve pressure on the ball of your foot as well as toe tip.
• To wear a splint to keep them in the right position.
• A surgical correction of toe deformity.