INTRODUCTION

Injuries to the fingers and thumb are a common reason for visits to primary care clinics and emergency departments. To care for such injuries well, clinicians must have a sound grasp of basic hand anatomy.

The basic clinically relevant anatomy of the fingers and thumb is reviewed here. Specific finger injuries and their management are discussed elsewhere. (See "Extensor tendon injury of the distal interphalangeal joint (mallet finger)" and "Flexor tendon injury of the distal interphalangeal joint (jersey finger)".)

NOMENCLATURE AND OVERALL STRUCTURE

Finger function involves a complex interaction among multiple joints, flexor and extensor tendons, and supporting fascia and ligaments [1-6]. Each of the digits, except the thumb, has three phalanges with three hinged joints: distal interphalangeal (DIP), proximal interphalangeal (PIP), and metacarpophalangeal (MCP) (figure 1). Joint stability is provided by the structure of the phalanges, joint capsule, radial and ulnar collateral ligaments and dorsal and palmar ligaments.

Flexion and extension are the primary movements of the fingers. Abduction and adduction can be performed at the MCP joints. The thumb is capable of opposition, abduction, adduction, and retropulsion, in addition to flexion and extension. The thumb is discussed below. (See 'Thumb anatomy' below.) Tables and diagrams summarizing the movements and innervation of the fingers and thumb are provided (figure 2 and figure 3 and figure 4 and table 1 and table 2 and table 3).

Fingers are referred to by naming and numbering systems, but names appear to cause less confusion among clinicians [7]. Throughout the UpToDate reviews dealing with fingers and hands, we use standard names to refer to fingers (ie, thumb, index, middle, ring, and little). It is important to note that while the anatomy described below is considered standard, considerable variation exists among individuals.