Last Updated on June 11, 2025
The phalanges of hand are the small tubular bones that form the skeletal framework of the fingers and thumb. These bones play a central role in the intricate movements of the hand, enabling grasping, pinching, and fine motor coordination.
Understanding phalanx anatomy is important as these bones are frequently involved in trauma, degenerative conditions, and tendon-related injuries. This article focuses on the detailed structure, attachments, joint relationships, and clinical relevance of the phalanges in the human hand.
Overview of Phalanges of Hand
The human hand consists of 14 phalanges.
- Proximal Phalanges (5 total): Each digit, including the thumb, begins with a proximal phalanx that articulates with the corresponding metacarpal bone.
- Middle Phalanges (4 total): Present in the index, middle, ring, and little fingers. The thumb lacks a middle phalanx.
- Distal Phalanges (5 total): Terminal bones of each digit. These support the fingertip pads and nails.
Each phalanx is composed of a base, shaft, and head (or tuft in the distal phalanges). Despite having a common structural plan, the phalanges vary in size, contour, and surface features depending on their anatomical level and function.
Distal Phalanx Anatomy
The distal phalanges are the terminal bones of each digit, forming the bony support for the fingertips and nail beds. These bones exhibit distinct anatomical features compared to the middle and proximal phalanges, particularly at their distal end, which flattens into a broad, roughened area known as the tuft.
This morphology provides anchorage for soft tissues and aids in sensory and functional precision.
These phalanges differ in size, shape, and contour from proximal and middle phalanges.
The distal phalanges of the middle and ring fingers are similar in length, followed by the length of the index and little finger. Except for the little finger, the width of all the distal phalanges is the same.
Parts of the Distal Phalanx
The distal phalanx consists of the following parts, from proximal to distal.
- Base
- Shaft
- Tuft or ungual tuberosity
Base
The base of the distal phalanx generally equals the head of the middle phalanx with which it articulates.
On the dorsal aspect base flares out dorsally and centrally, creating a ridge that separates the articular surface from the shaft.
The dorsal base is slightly roughened and forms a raised area called the dorsal tubercle.
Shaft
- The shaft is wide proximally and tapers distally, with the narrowest portion being just proximal to the tuft.
- It is generally thinner than those of the proximal or middle phalanges.
- The dorsal surface is slightly convex and smooth.
- Volar surface is slightly concave to accommodate soft tissue structures like the digital pulp.
- Medial and lateral surfaces are rounded, providing sites for ligamentous and fibrous insertions.
Tuft
Tuft is the terminal, thick, roughened crescent-shaped portion of the distal phalanx. The tuft provides for attachment of septae that support, stabilize, and anchor the pulp of the digit to the distal phalanx
- It anchors the fibrous septae of the digital pulp, stabilizing the soft tissue pad of the fingertip.
- On the dorsal side, it directly supports the germinal and sterile matrix of the nail.
- The volar tubercle provides insertion for the flexor digitorum profundus (or flexor pollicis longus in the thumb).
- Lateral tubercles (radial and ulnar) serve as attachment sites for the collateral ligaments.
- The extensor digitorum communis and related extensors insert dorsally at or near the tuft.
- Small branches of the proper digital arteries form a dorsal arcade near the base of the distal phalanx, just proximal to the nail fold.
- Ligamentous structures span from the lateral base to the margins of the tuft, reinforcing joint and pulp stability.
Digital Pulp
Digital pulp is a honeycomb structure of fibrous septae containing pockets of fat in each compartment. The proximal part of the pulp is thicker and more mobile than the distal pulp. Tuft is the anchoring point of the architecture of pulp.
The distal phalanx plays a crucial role in sensation, nail support, and fine motor control, including precision grip. Its shape and structure are adapted to resist pressure and shearing forces during fine motor tasks.
Middle Phalanx Anatomy
A middle phalanx [medial phalanx or intermediate phalanx] is a tubular bone that articulates with the distal phalanx distally and the proximal phalanx proximally.
Each middle phalanx has a head, body[shaft], and a base.
There is one middle phalanx in each finger, except the thumb, which has none.
Attachments
- Flexor digitorum superficialis tendons, along with the flexor sheath, are attached to the middle phalanges at their sides. In between, the flexor digitorum profundus crosses to attach to the distal phalanx.
- On the dorsal side, the extensor digitorum and associated tendons insert via the extensor expansion.
The middle phalanx plays a biomechanical role in both gripping and releasing functions, particularly contributing to the movement range at the PIP joint.
Proximal Phalanx
The proximal phalanges are the most basal bones of each digit, forming articulations with the corresponding metacarpal bones at the metacarpophalangeal (MCP) joints.
All five digits, including the thumb, contain a proximal phalanx. These are the longest of the phalangeal bones.
Proximal phalanges are the longest. The long shafts are flat on the palmar side, but convex dorsally and transversally. Additionally, the medial and lateral borders have distinct sharp edges for attachment.
Each proximal phalanx has three anatomical parts:
Base
- Articulates proximally with the head of the metacarpal bone.
- The articular surface is concave, allowing for flexion, extension, and limited rotation at the MCP joint.
- Provides attachment sites for the volar plate, collateral ligaments, and intrinsic hand muscles.
Shaft
- The shaft is elongated and cylindrical.
- Palmar (volar) surface: Flat or slightly concave to accommodate flexor tendon passage.
- Dorsal surface: Gently convex and overlain by the extensor tendons.
- The medial and lateral borders may have subtle ridges for fibrous sheath and ligament insertions.
Head
- It is rounded and convex.
- It forms the proximal side of the proximal interphalangeal (PIP) joint in the fingers and the interphalangeal (IP) joint in the thumb.
- It supports the base of the middle phalanx (or distal phalanx in the thumb).
Attachments
- The volar base receives insertions from intrinsic hand muscles:
- Lumbricals and interossei contribute to flexion at the MCP joint.
- Flexor brevis and abductor digiti minimi insert on the proximal phalanx of the little finger.
- The thumb’s proximal phalanx receives flexor pollicis brevis and abductor pollicis brevis on the volar side.
- Dorsally, the extensor digitorum and extensor pollicis brevis (thumb) attach to the extensor mechanism anchored to the proximal phalanx.
The proximal phalanges serve as the principal levers for finger movement at the MCP joints
Joints Involving Phalanges of Hand
Metacarpophalangeal (MCP) Joint
- Articulation between the convex head of the metacarpal and the concave base of the proximal phalanx.
- Classified as a condyloid synovial joint
- Allows
- Flexion and extension
- Abduction and adduction
- Limited circumduction
- Stabilized by:
- Collateral ligaments
- Volar (palmar) plate
- Dorsal extensor mechanism
Proximal Interphalangeal (PIP) Joint
- Formed between the convex head of the proximal phalanx and the concave base of the middle phalanx.
- Present in all fingers except the thumb.
- Classified as a hinge-type synovial joint (ginglymus)
- Allows flexion and extension
- Stabilized by
- Proper collateral ligaments (insert onto lateral tubercles of middle phalanx)
- Accessory collateral ligaments (attach to the volar plate)
- Volar plate
Distal Interphalangeal (DIP) Joint
- Formed between the convex head of the middle phalanx and the concave base of the distal phalanx.
- Present in all four fingers
- Hinge-type joint, functionally similar to the PIP joint.
- Stabilization similar to the PIP joint, involving:
- Collateral ligaments
- Volar plate
- Balanced action of the flexor digitorum profundus and the extensor mechanism
Thumb Interphalangeal (IP) Joint
- Articulation between the proximal and distal phalanges of the thumb.
- Hinge joint with similar anatomy and stability features as DIP and PIP joints in the fingers.
Blood Supply of the Phalanges
The vascular supply to the phalanges of the hand is derived primarily from the digital branches of the radial and ulnar arteries, which contribute to both the superficial and deep palmar arches. These arterial systems give rise to the proper palmar digital arteries, which travel along the sides of the fingers and provide segmental branches to each phalanx.
Functions of the Phalanges
- Grasping and Manipulation
- Pinching and Opposition movements
- Tip-to-tip pinch
- Lateral/key pinch
- These are critical for tasks like buttoning, turning keys, or picking up small objects.
- Tactile Sensory Feedback
- Nail Support and Protection
- Terminal levers in the hand’s kinetic chain, transmitting muscle forces from the forearm and intrinsic hand muscles to produce precise movements.
- Assist in postural balance and extension stability when the hand is weight-bearing (e.g., during crawling or certain support maneuvers).
Clinical Relevance of Phalanges
Phalanges of the hand are frequently involved in traumatic, inflammatory, and neoplastic conditions.
Injuries
Phalangeal injuries are common in sports, industrial accidents, and crush injuries. The phalanges of distal hand are more commonly injured as these are end organs for hand work and thus exposed everytime a work is performed.
- Fingertip injuries: Finger tips can be injured by getting caught as in doors or an object striking the fingers, as the hand protects from injury or crush injuries. Nail and nailbed injuries are common in crush injuries.
- Phalanx fractures: Most common fractures of the upper limb. A slight male preponderance is noted. Crush and blunt trauma are the most common causes
- Dislocations: Dislocations commonly involve the PIP and DIP joints. These can be dorsal as well as volar dislocationa
- Tendon Injuries: Both extensor and flexor tendons are at at wrist of being injured by sharp injury or crush injury.
- Mallet Finger
- Caused by avulsion of the extensor tendon from the dorsal base of the distal phalanx.
- Results in inability to extend the DIP joint actively.
Arthritis
Iinterphalangeal joints are involved in osteoarthritis, rheumatoid arthritis and other types of arthritides
- Osteoarthritis (OA)
- DIP joints (Heberden’s nodes) and PIP joints (Bouchard’s nodes).
- Rheumatoid Arthritis (RA)
- Typically affects MCP and PIP joints, sparing the DIP joints.
- Psoriatic Arthritis
- May involve any interphalangeal joint, often with DIP joint predilection.
- Can cause “pencil-in-cup” deformities on imaging.
Tumors and Cystic Lesions
- Enchondroma is a common tumor of the phalanges
- Epidermoid Inclusion cysts are common in finger tips due to frequent piercing injuries
- Glomus Tumor is a painful, subungual lesion involving vascular structures of the distal phalanx.
Other Clinical Considerations
- Infections such as a felon or osteomyelitis
- Growth plate injuries in pediatric patients
- Congenital anomalies like brachydactyly or syndactyly often involve phalanges.
Sources
A list of key peer-reviewed studies, textbooks, and clinical references used in preparing this article is provided below for transparency and professional context.
- Zancolli E, Cozzi EP. Atlas of Surgical Anatomy of the Hand. New York: Churchill Livingstone; 1992.
- Chang J, Valero-Cuevas F, Hentz VR, Chase RA. Anatomy and Biomechanics of the Hand. Mathes ed. Plastic Surgery. Philadelphia: Elsevier; 2006. 7:
- Chan O, Hughes T. Hand. BMJ. 2005 May 7;330(7499):1073-5. doi: 10.1136/bmj.330.7499.1073. [PubMed]
- Porter N, Khan SH. Radiology of acute injuries to the hand and fingers. Br J Hosp Med (Lond). 2010 Sep;71(9):M134-6. [PubMed]
