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Lateral nail fold (hand)

The lateral nail fold is the soft-tissue elevation of skin along the sides of the fingernail, forming the protective periungual boundary of the nail plate. It anchors the skin to the distal phalanx via fibrous septa and provides a barrier against external trauma and infection.

The fold helps stabilize the nail plate, guide its growth, and protect the underlying nail matrix and bed. Its composition includes skin, dermis, dense fibrous tissue, small vessels, and sensory nerve endings, forming part of the paronychium.

Synonyms

  • Lateral paronychial fold

  • Lateral nail margin

  • Periungual fold

Location and Structure

  • Positioned on the lateral sides of the nail plate, extending from the proximal nail fold to the distal fingertip margin.

  • Structured as a skin ridge with underlying fibrous tissue anchoring it to the distal phalanx.

  • Forms the lateral walls of the nail groove where the nail plate slides during growth.

  • Composed of keratinized epidermis, dermis, and dense connective tissue.

  • Continuous with the proximal nail fold proximally and the fingertip pulp distally.

MRI Appearance

T1-weighted images:

  • Lateral nail fold appears as intermediate signal intensity soft tissue

  • Surrounding fat: bright

  • Nail plate: low signal (dark)

  • Distal phalanx cortex: very dark, marrow bright

T2-weighted images:

  • Soft tissue fold shows intermediate-to-bright signal depending on hydration

  • Nail plate remains low signal

  • Subcutaneous fat appears relatively bright

  • Clear distinction between fold, nail plate, and distal phalanx

STIR:

  • Lateral nail fold: intermediate-to-dark normal signal

  • Fat entirely suppressed

  • Enhances visibility of soft-tissue layers and margins

MRI image

Lateral nail fold hand MRI axial image-img-00000-00000