What causes thickened toenails?
Nails can become thickened due to repetitive trauma or damage to the nail bed. Incorrectly fitting shoes can cause the toes to bang repetitively against the end of the shoe causing microtrauma. If you have dropped or kicked a particular toe it can cause damage to the nail bed causing it to grow back thicker permanently. In some cases, the way that a person walks can contribute to thickening of the toenails (for example if a person has developed claw toes due to their walking style, the toes will absorb the ground reaction forces through the end of the toes which can causes thickening of the toenails and corns/calluses on the ends of the toes). Age related changes can also cause nails to thicken.
What can be done for thickened toenails?
A podiatrist can cut thickened toenails and thin the nails with a burr to make them more manageable and comfortable. As the nail re-grows it may require thinning again.