Trauma, especially repetitive trauma like running, will cause onycholysis, or the toenail falling off. This trauma may be completely painless. I find it commonly on the second toe in runners, and in the fourth toe in those wearing more pointy, fashionable shoes. Running shoes may be too big, and the sliding of the toe into the edge of the shoe can cause this. Shoes that are too small may cause this as well. The big toe can be affected. Also, trauma increases the likelihood of a fungal infection invading the toenail, which is a painless condition. A person with this condition would notice their nail thickening before it lifted off the nail bed.
The tendency to have fungal nails is definitely inherited, so this may also be a cause of the loss of your client’s toenail. A podiatry visit is recommended, so the nail can be helped to grow back cosmetically. Once a nail is damaged, the matrix can also be damaged. A timely visit to the podiatrist can help grow the nail back without incident.
— Johanna Youner, D.P.M., is attending podiatric physician and surgeon at New York Downtown Hospital and is also in private practice in New York City.