Interphalangeal Joints of the Hand

This article or area is currently under construction and may only be partially complete. Please come back soon to see the finished work! (21/10/2020)

Original Editor - User Name

Top Contributors - Denys Nahornyi, Kim Jackson, Lucinda hampton, Shaimaa Eldib and Aminat Abolade

Description

The interphalangeal joints of the hand are the hinge joints between the phalanges of the fingers that provide flexion towards the palm of the hand.

Anatomy

There are two sets in each finger (except in the thumb, which has only one joint):

"proximal interphalangeal joints" (PIJ or PIP), those between the first (also called proximal) and second (intermediate) phalanges "distal interphalangeal joints" (DIJ or DIP), those between the second (intermediate) and third (distal) phalanges Anatomically, the proximal and distal interphalangeal joints are very similar. There are some minor differences in how the palmar plates are attached proximally and in the segmentation of the flexor tendon sheath, but the major differences are the smaller dimension and reduced mobility of the distal joint.[1]

Articulating Surfaces

Each interphalangeal joint is composed of the head of the more proximal phalanx and the base of its distal counterpart. This means that, for example, the proximal interphalangeal joint is formed by the union of the head of the proximal phalanx with the base of the middle phalanx. This same pattern applies to the distal interphalangeal joint, meaning that it is formed by the articulation of the head of the middle phalanx with the base of the distal phalanx.

Closer inspection of the phalangeal head reveals two curved condylar processes with a shallow groove in between. These condyles are received by two concavities of reciprocal size and shape on the base of the distally lying phalanx. Between these two concavities is a raised ridge of bone that glides within the groove of the phalangeal head, promoting intraarticular stability. These joint surfaces are covered by a layer of hyaline cartilage that extends further palmarly than dorsally, creating a proximal articular surface which is greater than the distal surface. Unlike the metacarpophalangeal joints, there is little articular surface on the dorsal aspect, and therefore little hyperextension. 

The point of articulation does not occur directly at the apex of the condylar processes, but rather on their inner sloping surfaces. This results in the radii of the condyles of the phalangeal head being greater than that of the convex surfaces of the phalangeal base, leaving the joint markedly incongruent. This incongruency manifests as a small intercondylar joint space in most people.

Ligaments & Joint Capsule

Surrounding each interphalangeal joint is a fibrous joint capsule, the inner lining of which is comprised of a synovial membrane. Strengthening each joint capsule are two collateral ligaments and a palmar ligament, also known as a palmar/volar plate. Dorsally, the joint capsule is strengthened by a broadening of the extensor tendons. This extensive ligamentous contribution to each joint capsule increases the articular surface of the phalangeal base, improving joint congruence.

Collateral ligaments

The collateral ligaments course on either side of each interphalangeal joint, arising from the head of the more proximal phalanx and extending to the palmar, or volar, aspect of its distal counterpart. Arising from each collateral ligament is an accessory ligament, which extends anteriorly to attach to the fibers of the palmar ligament. These ligaments help to prevent excessive adduction-abduction movements of the interphalangeal joints.

Palmar ligament

The palmar ligament (a.k.a palmar/volar plates) is a thick plate of fibrocartilage located on the palmar surface of each interphalangeal joint. This ligament has a characteristic upside down “U” shape, with its distal part arching across the base of the distally lying phalanx to blend with the accessory collateral ligaments. Proximally, the legs of the palmar ligament blend in with the periosteum of the body of the more proximally lying phalanx. These are termed ‘check rein’ ligaments and serve to prevent excessive hyperextension of the joint.

References

References will automatically be added here, see adding references tutorial.