Interphalangeal joints
Encyclopedia
The interphalangeal articulations of the hand are the hinge joint
s between the phalanges of the hand
(i.e. the finger bones).
There are two sets (except in the thumb
):
Anatomically, the proximal and distal interphalangeal articulations are very similar. There are some minor differences in how the volar 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.
.
At the level of the PIP joint the extensor mechanism splits into three bands. The central slip attaches to the dorsal tubercle of the middle phalanx near the PIP joint. The pair of lateral bands, to which contribute the extensor tendons, continue past the PIP joint dorsally to the joint axis. These three bands are united by a transverse retinacular
ligament, which runs from the palmar border of the lateral band to the flexor sheath at the level of the joint and which prevents dorsal displacement of that lateral band. On the palmar side of the joint axis of motion, lies the oblique retinacular ligament [of Landsmeer] which stretches from the flexor sheath over the proximal phalanx to the terminal extensor tendon. In extension, the oblique ligament prevents passive DIP flexion and PIP hyperextension as it tightens and pulls the terminal extensor tendon proximally.
and keratan sulfate
in the dorsal and volar plates is important in resisting compression forces against the condyles of the proximal phalanx. Together these structures protect the tendons passing in front and behind the joint. These tendons can sustain traction forces thanks to their collagen fibers.
On both sides it is reinforced by the so called check rein ligaments. The accessory collateral ligaments (ACL) originate at the proximal phalanx and are inserted distally at the base of the middle phalanx below the collateral ligaments.
The accessory ligament and the proximal margin of the volar plate are flexible and fold back upon themselves during flexion. The flexor tendon sheaths are firmly attached to the proximal and middle phalanges by annular pulleys A2 and A4, while the A3 pulley and the proximal fibres of the C1 ligament attach the sheaths to the mobile volar ligament at the PIP joint. During flexion this arrangement produces a space at the neck of the proximal phalanx which is filled by the folding volar plate.
The palmar plate forms a semi-rigid floor and the collateral ligaments the walls in a mobile box which moves together with the distal part of the joint and provides stability to the joint during its entire range of motion. Because the volar plate adheres to the flexor digitorum superficialis
near the distal attachment of the muscle, it also increases the moment of flexor action. In the PIP joint, extension is more limited because of the two so called check-rein
ligaments, which attach the volar plate to the proximal phalanx.
and extension
.
The muscles generating these movements are:
! Location
! Flexion
! Extension>
| the flexor digitorum profundus acting on the proximal and distal joints, and the flexor digitorum superficialis acting on the proximal joints
| mainly by the lumbricals
and interossei
, the long extensors having little or no action upon these joints>
| the flexor pollicis longus
| the extensor pollicis longus>
The relative length of the digit varies during motion of the IP joints. The length of the palmar aspect decreases during flexion while the dorsal aspect increases by about 24 mm. The useful range of motion of the PIP joint is 30-70°, increasing from the index finger to the little finger. During maximum flexion the base of the middle phalanx is firmly pressed into the retrocondylar recess of the proximal phalanx, which provides maximum stability to the joint. The stability of the PIP joint is dependent of the tendons passing around it.
Hinge joint
A hinge joint is a bone joint in which the articular surfaces are molded to each other in such a manner as to permit motion only in one plane—backward and forward—the extent of motion at the same time being considerable....
s between the phalanges of the hand
Phalanges of the hand
The phalanges of the hand are commonly known as the finger bones. They are fourteen in number, three for each finger, and two for the thumb.Each consists of a body and two extremities....
(i.e. the finger bones).
There are two sets (except in the thumb
Thumb
The thumb is the first digit of the hand. When a person is standing in the medical anatomical position , the thumb is the lateral-most digit...
):
- "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 and third (distal) phalanges
Anatomically, the proximal and distal interphalangeal articulations are very similar. There are some minor differences in how the volar 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.
Joint structure
The PIP joint exhibits great lateral stability. Its transverse diameter is greater than its antero-posterior diameter and its thick collateral ligaments are tight in all positions during flexion, contrary to those in the metacarpophalangeal jointMetacarpophalangeal joint
The metacarpophalangeal joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the first phalanges, with the exception of that of the thumb, which presents more of the characters of a ginglymoid joint...
.
Dorsal structures
The capsule, extensor tendon, and skin are very thin and lax dorsally, allowing for both phalanx bones to flex more than 100° until the base of the middle phalanx makes contact with the condylar notch of the proximal phalanx.At the level of the PIP joint the extensor mechanism splits into three bands. The central slip attaches to the dorsal tubercle of the middle phalanx near the PIP joint. The pair of lateral bands, to which contribute the extensor tendons, continue past the PIP joint dorsally to the joint axis. These three bands are united by a transverse retinacular
Retinaculum
Occurs where in some places, groups of tendons from separate muscle pass under a band of connective tissueRetinaculum, from the Latin verb retinere , plural: retinacula may be:* In the wrist:** Flexor retinaculum of the hand...
ligament, which runs from the palmar border of the lateral band to the flexor sheath at the level of the joint and which prevents dorsal displacement of that lateral band. On the palmar side of the joint axis of motion, lies the oblique retinacular ligament [of Landsmeer] which stretches from the flexor sheath over the proximal phalanx to the terminal extensor tendon. In extension, the oblique ligament prevents passive DIP flexion and PIP hyperextension as it tightens and pulls the terminal extensor tendon proximally.
Volar structures
In contrast, on the palmar side, a thick ligament prevents hyperextension. The distal part of the volar ligament, called the volar plate, is 2 to 3 mm (0.078740157480315 to 0.118110236220472 in) thick and has a fibrocartilaginous structure. The presence of chrondroitinChondroitin sulfate
Chondroitin sulfate is a sulfated glycosaminoglycan composed of a chain of alternating sugars . It is usually found attached to proteins as part of a proteoglycan. A chondroitin chain can have over 100 individual sugars, each of which can be sulfated in variable positions and quantities...
and keratan sulfate
Keratan sulfate
Keratan sulfate , also called keratosulfate, is any of several sulfated glycosaminoglycans that have been found especially in the cornea, cartilage, and bone. It is also synthesized in the central nervous system where it participates both in development and in the glial scar formation following an...
in the dorsal and volar plates is important in resisting compression forces against the condyles of the proximal phalanx. Together these structures protect the tendons passing in front and behind the joint. These tendons can sustain traction forces thanks to their collagen fibers.
Volar ligament
The volar ligament (also called the palmar ligament) is thinner and more flexible in its central-proximal part.On both sides it is reinforced by the so called check rein ligaments. The accessory collateral ligaments (ACL) originate at the proximal phalanx and are inserted distally at the base of the middle phalanx below the collateral ligaments.
The accessory ligament and the proximal margin of the volar plate are flexible and fold back upon themselves during flexion. The flexor tendon sheaths are firmly attached to the proximal and middle phalanges by annular pulleys A2 and A4, while the A3 pulley and the proximal fibres of the C1 ligament attach the sheaths to the mobile volar ligament at the PIP joint. During flexion this arrangement produces a space at the neck of the proximal phalanx which is filled by the folding volar plate.
The palmar plate forms a semi-rigid floor and the collateral ligaments the walls in a mobile box which moves together with the distal part of the joint and provides stability to the joint during its entire range of motion. Because the volar plate adheres to the flexor digitorum superficialis
Flexor digitorum superficialis muscle
Flexor digitorum superficialis is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints....
near the distal attachment of the muscle, it also increases the moment of flexor action. In the PIP joint, extension is more limited because of the two so called check-rein
Bearing rein
A bearing rein, known today as an overcheck or a checkrein, is a piece of horse tack that runs from a point on the horse's back, over the head, to a bit. A bearing rein is used to prevent the horse from lowering its head beyond a fixed point...
ligaments, which attach the volar plate to the proximal phalanx.
Movements
The only movements permitted in the interphalangeal joints are flexionFlexion
In anatomy, flexion is a position that is made possible by the joint angle decreasing. The skeletal and muscular systems work together to move the joint into a "flexed" position. For example the elbow is flexed when the hand is brought closer to the shoulder...
and extension
Extension (kinesiology)
In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...
.
- Flexion is more extensive, about 100°, in the PIP joints and slightly more restricted, about 80°, in the DIP joints.
- Extension is limited by the volar and collateral ligaments.
The muscles generating these movements are:
! Flexion
! Extension>
| the flexor digitorum profundus acting on the proximal and distal joints, and the flexor digitorum superficialis acting on the proximal joints
| mainly by the lumbricals
Lumbricals of the hand
The lumbricals are intrinsic muscles of the hand that flex the metacarpophalangeal joints and extend the interphalangeal joints.-Structure:There are four of these small, worm-like muscles on each hand. These muscles are unusual in that they do not attach to bone...
and interossei
Interossei
Interossei refer to muscles between certain bones. There are many interossei in a human body. Specific interossei include:-On the hands:* Dorsal interossei muscles of the hand* Palmar interossei muscles-On the feet:...
, the long extensors having little or no action upon these joints>
| the flexor pollicis longus
| the extensor pollicis longus>
The relative length of the digit varies during motion of the IP joints. The length of the palmar aspect decreases during flexion while the dorsal aspect increases by about 24 mm. The useful range of motion of the PIP joint is 30-70°, increasing from the index finger to the little finger. During maximum flexion the base of the middle phalanx is firmly pressed into the retrocondylar recess of the proximal phalanx, which provides maximum stability to the joint. The stability of the PIP joint is dependent of the tendons passing around it.
See also
- FingerFingerA finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....
- Interphalangeal articulations of footInterphalangeal articulations of footThe interphalangeal articulations of the foot are the joints between the phalanges of the toes. They are ginglymoid joints, and each has a plantar and two collateral ligaments...
- Metacarpophalangeal jointMetacarpophalangeal jointThe metacarpophalangeal joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the first phalanges, with the exception of that of the thumb, which presents more of the characters of a ginglymoid joint...