Medically reviewed by Casey Gallagher, MD Ridges in nails can develop due to a current or past illness or injury. A healthy ...

Fingernail ridges are raised lines or grooves that affect one or more fingernails and may run vertically or horizontally. Vertical ridges, or longitudinal ridges, are the most common type.

You may have splinter hemorrhages if you have dark, vertical lines under your nails that look like splinters. The most common cause is trauma to the nail. Splinter hemorrhages can also happen due ...