I. Osteoarticular anatomy of the wrist joint The wrist joint consists of 8 carpal bones, the bases of the 1st-5th metacarpal bones, and the distal radial-ulnar bones, which form the distal radial-ulnar joint, radial-ulnar carpal joints, the midcarpal joints, the carpometacarpal joints, and the intercarpal joints, respectively. (Figure 1-slide 2) The distal radial-ulnar joint consists of a vertical portion and a transverse portion. The vertical portion consists of the ulnar notch of the radius and the circumferential articular surface of the ulnar head, and the transverse portion consists of the ulnar head and the Triangle Fibrous Cartilage (TFC). (Figures 2 – 3) According to the difference in anatomical length between the distal ulna and the distal radius, there is a positive ulnar variant: the distal ulna is longer than the distal radius, a negative ulnar variant: the distal ulna is shorter than the distal radius, and a neutral ulnar variant: the distal radius and ulna are equal in length. (Figure 3-slide 5) Normal: positive varus is +2 mm, negative varus is -4 mm. ulnar varus is biomechanically important for the wrist joint, altering the axial load between the radial and ulnar bones, radial-ulnar-ulnar joint contact pressures, and lunate surface stresses. In the case of neutral ulnar varus, about 80% of the distally transmitted stresses are distributed in the radial carpal joint and about 20% in the ulnar carpal joint. Some basic and clinical studies have suggested that ulnar varus is closely related to ischemic necrosis of the lunate, ulnar-wrist impingement syndrome, and distal radial-ulnar joint stability. The Triangle FibrousCartilage Complex (TFCC-Triangle FibrousCartilage Complex) is more complex in composition, with triangular fibrocartilage, ulnar carpal meniscus, ulnar collateral ligament of the wrist, palmar radial-ulnar ligament, dorsal radial-ulnar ligament, and ulnar extensor carpi radialis brevis tendon sheath. (Figure 4 – Slide 7) The main roles of the TFCC include, cushioning the ulnar side of the wrist from stress effects, separating the distal radial-ulnar joint from the radial-wrist joint, connecting the radius and ulna, and stabilizing the distal radial-ulnar joint. The radial carpometacarpal joint is a biaxial elliptical or condylar joint consisting of the navicular, lunate, and triquetrum (elliptical articular surfaces) and the articular surfaces of the distal radius and triangular fibrocartilage, which are not interconnected with the midcarpal and distal radial-ulnar joints (separated by the interosseous ligaments of the carpal bones and the triangular fibrocartilage). (Fig. 5-slide 11) The joint capsule is thin and loose, reinforced by intra- and extracapsular ligaments. The midcarpal joint consists of two rows of carpal bones on the distal and proximal sides, resembling an S-shape. The radial portion is the navicular bone and the large and small polygonal bones (i.e., the STT joint), which resembles a sliding joint with a small range of motion; the ulnar portion is the capitellum, the hook bone, and the navicular, lunate, and deltoid bones, which resembles a condylar joint with a large range of motion. (Figure 6 – slide 14) The proximal row of carpal interosseous joints include, navicular-lunate joint: the proximal medial surface of the navicular bone is composed of the lateral surface of the lunate bone, which is connected by the navicular-lunate interosseous ligament (SLIL); lunate-triquetral joint: the medial surface of the lunate bone is composed of the underside of the triquetrum bone, which is connected by the lunate-triquetral interosseous ligament (LTIL); and the pea-triquetral joint: the palmar surface of the triquetrum bone is composed of the dorsal surface of the pea bone, which is composed of the capsule being lax and reinforced by the peripheral ligaments and tendons. Reinforced, the pea bone has tendon and ligament attachments, similar to the patella, and plays a role in stabilizing the ulnar side of the wrist. (Figure 7 – slide 17) The distal interphalangeal joint consists of the greater and lesser trochanter, the capitellum, and the hook bone connected by adjacent interosseous ligaments (greater and lesser trochanter, lesser trochanter, and capitellar hook bone ligaments). The distal interphalangeal joint has very little amplitude of movement, and is almost a single unit of motion, so that ligamentous tears are very unlikely to occur. (Fig. 7 – Mirage 17) 1st carpometacarpal joint: consists of the greater trochanter and the base of the 1st metacarpal, saddle-shaped joint, the joint capsule is thick and loose, the joint capsule is reinforced by ligaments around the joint capsule, the joint is flexible, stable, and can accomplish a wide range of activities in multiple directions. (Figure 8-slide 18) 2C5 carpometacarpal joint: composed of the base of the 2C5 metacarpal bone and the small polygonal bone, capitate bone, hook bone, of which the 2nd and 3rd carpometacarpal joints are very stable with minimal mobility; the 5th carpometacarpal joint is more mobile, second only to the 1st carpometacarpal joint, and also saddle joint, and its capsule is more lax than that of the 2nd, 3rd and 4th carpometacarpal joints, and the capsule around the 2nd and 3rd carpometacarpal joints is strengthened by the carpal metacarpal dorsolateral ligament and the intercalary ligament. The capsule of the 2C5 carpometacarpal joint is surrounded by the dorsal carpometacarpal ligament and the interosseous ligament. (Fig. 8-slide 20) The blood supply to the wrist is provided by the radial, ulnar, and interosseous arteries. Wrist movements are controlled and coordinated through the muscles (tendons) of the wrist, which also play an important role in the stability of the wrist. Flexors: radial-ulnar flexor (tendon), palmaris longus (tendon), extensors: radial and ulnar extensor carpi radialis (tendon), flexors: flexor hallucis longus (tendon), superficial deep flexor extensor digitorum superficialis (tendon), extensor digitorum longus (tendon), extensor digitorum superficialis (tendon), extensor digitorum longus (tendon), extensor digitorum superficialis (tendon), extensor digitorum longus (tendon), extensor digitorum superficialis (tendon), extensor digitorum longus (tendon), and extensor digitorum totalis (tendon). （Carpal ligaments Classification: According to the starting and ending points of the ligaments, they are divided into extrinsic ligaments, which are located between the carpal bones and the radius, ulna, or metacarpals, and intrinsic ligaments, which start and end between the carpal bones; and according to the articular parts, they are divided into the radial carpal ligaments, middle carpometacarpal ligaments, carpal-metacarpal ligaments, dorsal carpometacarpal ligaments, and intercarpal articular ligaments. Function: Provide mechanical support for the wrist joint, control and regulate the movement of the wrist joints, maintain the stability of the wrist joint and ensure the completion of the wrist joint function. Palmar radial carpal ligament (Figure 10 – slide 28) Radial collateral ligament or radial navicular ligament (Radioscaphoid Ligament – RSL): originates from the dorsal side of the radial tuberosity and ends at the navicular tuberosity Radial navicular head ligament (Radioscaphocapitate Ligament – RSCL): originates from the radial tuberosity and the distal palmar labrum of the radius, and stops distally at the navicular girdle and head. Long Radiolunate Ligament (LongRadiolunate Ligament-LRL): originates from the palmar lip of the distal radius and ends at the radial margin of the metacarpal surface of the lunate Short Radiolunate Ligament (ShortRadiolunate Ligament-SRLL): originates from the metacarpal margin of the distal lunate fossa of the radius and stops at the metacarpal surface of the lunate, which is thought to be a thickening of the carpal capsule only. Thickening of the carpal capsule Radioscapholunate Ligament (Radioscapholunate Ligament-RSLLorLigamentof Testut): deep ulnar surface of the radioscapholunate ligament, originating on the palmar surface of the intercondylar ridge of the distal radial carpal articular surface of the radius, ending on the palmar surface of the proximal pole of the navicular bone and intertwining with the navigational ligament of the navicular lunate and, to a lesser extent, ending on the palmar surface of the lunate at its radial border The metacarpophalangeal ulnar carpal ligament (Figs. Ulnolunate ligament (ULL): begins on the palmar aspect of the distal ulna, continues with the SRL, and terminates at the palmar pole of the lunate Ulnodistal ligament (CUTL): lies on the ulnar aspect of the UL, has the same starting point as the other metacarpal ulnocarpal ligaments, and terminates on the proximal metacarpal surface of the triquetrum Ulnocapitate ligament (CUTL): is located on the ulnar aspect of the UL, and terminates at the proximal metacarpal surface of the triquetrum Ulnocapitate ligament (UCL): is located on the metacarpal aspect of the UL. The ulnocapitate ligament (CUCL): begins at the base of the ulnar styloid process and the palmar surface of the radial-ulnar ligament, and ends at the skull and its adjacent interosseous ligament The dorsal radiocarpal ligament (DRCL): begins at the dorsal margin of the articular surface of the distal radius and is relatively broad, crossing the dorsal surfaces of the lunotriquetral bone, navicular-lunar joint, and triquetrum, and ending at the dorsal surface of the triquetrum. It crosses the dorsal surface of the lunate, navicular, and lunotriquetral joints and ends at the dorsal surface of the triquetrum. (Fig. 12 – Mirage 32) Dorsal Intercarpal Ligament (DICL): originates at the dorsal surface of the triquetrum, continues radially from the DRC stop, and terminates at the girdle of the navicular bone and the greater and lesser trochanters. (Figure 12-phantom 32) Metacarpal median carpal ligament (Figure 13-phantom 34) Navicular small and large polygonal ligaments (Scaphotrapezium TrapezoidLigament-STTL): originates at the distal pole of the navicular bone and stops at the palmar aspect of the large and small polygonal bones Navicular capitate ligament (Scaphocapitate Ligament-SCL): originates at the distal pole of the navicular bone and ends at the body of the skull. Triquetrocapitate Ligament (TCL): originates from the metacarpal surface of the triquetrum and terminates at the body of the skull Triquetrohamate Ligament (THL): originates from the metacarpal surface of the triquetrum and terminates at the metacarpal surface of the hookbone Pisohamate Ligament (PHL): originates from the ulnar carpal flexor tendon and terminates at the metacarpal surface of the hookbone. Pisohamate Ligament (PHL): continuation of the ulnar flexor tendon, starting at the distal end of the calcaneus and ending near the hook of the hook bone Interosseous Ligament of the proximal carpal bones Scapholunate Interosseous Ligament (SLIL): divided into three parts: dorsal portion – between the dorsal aspect of the proximal medial surface of the navicular bone and the dorsal angle of the lateral surface of the lunate bone, proximal portion – located on the proximal side of the navicular and lunate joints, the ligament is in contact with the articular cartilage at the point of attachment to the lunate bone, and is connected to the articular cartilage by the proximal portion of the ligament. The proximal portion – located on the proximal side of the navicular joint, the ligament fuses with the articular cartilage at the point of attachment to the navicular bone, the palmar portion – located on the palmar side of the navicular joint – is thinner than the dorsal portion, and there is no ligamentous attachment to the distal portion of the navicular joint. (Fig. 13 – Mirage 36) Lunotriquetral Interosseous Ligament (LTIL): located between the lunotriquetral bones, divided into palmar, dorsal and proximal portions, the palmar side is thicker than the dorsal side. (Figure 14 – slide 38) Navicular Triangular Ligament? （Scaphotriquetral Interosseous Ligament (STIL): dorsal portion – originates dorsal to the lumbar aspect of the navicular bone, passes through and attaches to the dorsal pole of the lunate bone, and terminates dorsal to the triquetrum; metacarpal portion – originates distal to attachment point of the navicular-lunate ligament of the navicular bone and terminates metacarpal to the triquetrum; Pisotriquetral Ligament (PTIL): located between the lunate and triquetrum. Pisotriquetral ligament-PTL Distal intercarpal ligament (Fig. 15 – slide 41) Trapezium Trapezoid Interosseous LigamentCTTIL: transverse ligament bundle, located between the greater and lesser trochanter, divided into palmar and dorsal parts. TrapeziocapitateInterosseousLigament- TCIL): the ligament is divided into palmar, dorsal and deep parts, the first two parts start from the medial side of the small polygonal bone and end with the body of the skull. Capitohamate Interosseous Ligament (CHIL): divided into palmar, dorsal and deep parts, the first two parts start from the medial side of the skull and end at the lateral side of the hook bone. The distal carpometacarpal joint space is narrow, and the interosseous ligament is short and tough, and is considered to be a kinematic whole. The carpometacarpal joint and interphalangeal ligament ligaments (Fig. 16 – slide 42) III. Kinematics of the wrist The wrist joint is a kinematic connection system whose motion is not limited to the flexion-extension and radial-ulnar planes, but is actually a multidirectional, universal joint, with synchronized and coordinated action between the carpal bones under the guidance and restraints of the complex system of intrinsic and extrinsic ligaments, as well as under the kinetic effect of the muscles of the forearm. Through a complex biomechanical process, it coordinates the change of position between the hand and forearm, and transmits the power of the muscles to the hand, and ultimately completes the hand function perfectly. Therefore, the wrist joint is one of the most important guarantees for the completion of hand function, and the completion of wrist function depends on the unique kinematic behavior of the carpal bones, the morphology of the carpal bones (including the distal end of the radial-ulnar bones), the integrity of the carpal ligaments, and the functional status of the related muscles. The study of the kinematic patterns of the carpal joint in physiological and pathophysiological states is of great significance in understanding the injury mechanisms of carpal instability. The traditional concept that the distal and proximal rows of carpal bones are each a relatively fixed system and that their motion occurs at the midcarpal and radial carpal joints, i.e., between the distal and proximal carpal bones, and between the proximal and distal radial-ulnar articulating surfaces (Johnston 1907), ignores an important issue, that is, the intercarpal motion (Henke 1859). With continued research and discovery, the importance of intercarpal motion (Virchow 1902) in the biomechanical mechanism of the wrist joint became increasingly emphasized. With this, various theories or models of carpal kinematics have arisen. The threebarlinkage system or central chain system (Gilford 1943) views the radius-lunate-cranial complex as a central chain system (including two single hinge joints), in which the lunate is in an unstable state as an intercalated element, and the navicular bone is located on the lateral flank of the chain, acting as a stabilizer. stabilizes the chain. (Figure 17-slide 46) Later, this theory was further extended and enriched to form the slide crankmechanism (Fisk 1970, Linscheid 1972), which emphasizes the “crank” stabilizing effect of the navicular bone on the central chain, with the navicular bone spanning into the mid-wrist joint to avoid loads. This theory emphasizes the “cranking” stabilizing effect of the navicular bone on the central chain, with the navicular bone spanning into the midcarpal joint to avoid collapse of the kinematic chain under load, but it gives less consideration to the role of the special geometry of the carpal bones, especially the geometry of the proximal carpal bones, and the interaction of the carpal bones under the ligamentous connection in the kinematics of the carpal joint. The “mechanical column” theory (Navarro 1921), on the other hand, proposes a longitudinal column model of the wrist joint, which suggests that there are three mechanical columns in the wrist joint: the lateral, or kinematic, column, which refers to the navicular bone and the greater and lesser trochanters, whose main role is to support the thumb and conduct loads between the two rows of carpal bones, and the central, or flexion-extension, column, which refers to the lunate, capitate, and hook bones, palmar flexion and dorsal extension, and the dorsal flexion and dorsal extension. Taleisnik (1976) concluded that the pea bone does not play a role in wrist motion and should be removed from the medial column, and that there is little motion between the distal rows of carpal bones, which are a complete motor unit, and therefore the greater and lesser polypi should be merged into the central column (Fig. 18-phantom 49). (Fig. 18-slide 49) The “ellipsoidal ring” theory (Lichtman 1981) suggests that the carpal joint resembles a transverse ring consisting of four separate segments: the distal carpal bones, navicular, lunate, and triquetrum. Each link is connected to the links on either side of it by ligaments. Continuity of the ligaments ensures synchronized and coordinated movement of the carpal joint. A rupture of any of these links results in wrist dysfunction, and this theory emphasizes the importance of the proximal row of carpal bones, especially the reciprocal movement between the carpal bones (the intercarpal ligaments).Weber, on the other hand, held a different theory of the columnar arrangement of the carpal bones. He divided the carpal bones into two columns: the radial load-bearing column of carpal bones, consisting of the lunate, capitate, navicular, and lesser trochanter; and the ulnar control column of carpal bones, consisting of the triquetrum and hook bones. The spiral triangular hook joint is the key to determining carpal joint position during load changes. The geometry of the lunate is one of the most important aspects of the carpal bones (Kauer 1980). Metacarpal-dorsal: the metacarpal pole is larger than the dorsal pole distally and proximally, and is wedge-shaped in the sagittal plane, with the cuneiform pattern gradually becoming less pronounced from the radial to the ulnar side; radial-ulnar: the same wedge pattern, with the radial side smaller than the ulnar side; the above geometrical pattern determines that the lunate can easily rotate toward the dorsal and ulnar sides. The geometry of the lunate itself and the mutual stabilization provided by the navicular and triangular bones together determine the position and movement of the lunate between the skull and radius. The interaction between the carpal bones, especially the proximal carpal bones, plays an important role in wrist motion and stability. The proximal carpal bones are maintained in mechanical integrity by the intercarpal ligaments, and the lunate is considered to be a rotational (torsional) spacer between the navicular and deltoid bones (Ruby 1987, Horri 1991, Ritt 1995), which is in a state of equilibrium in the motion generated by the navicular intercarpal ligaments (flexion) and the lunotriquetral intercarpal ligaments (straightening), while the deltoid bone is an insertion of the ulnar carpal chain with very limited contact with the ulnar joint surfaces. Contact with the articular surface of the ulna is very limited. The motion of the triquetrum is consistent with that of the lunate due to the same wedge direction in the sagittal plane as the lunate, and its motion or stabilization is related to that of the navicular lunate, as well as to the characteristics of its contact with the midcarpal joints, such as dorsal rotation of the triquetrum when the lunate-triquetrum separates, and metacarpal rotation of the navicular lunate. Under normal conditions, the distal end of the navicular bone is in contact with the large and small polygonal bones and the skull, and the proximal end is placed between the skull and the radius, and the navicular bone itself is in a palmar-flexed posture; when the navicular-lunar separation occurs, the triangular bone and the lunate bone are dorsally extended at the same time, while the navicular bone is palmar-flexed. When the size of the multicoronary and the distance between the radius decreases (carpal metacarpal flexion and radial deviation), the navicular bone is in palmar flexion (rotation), and conversely, the navicular bone is in dorsiflexion, and the mechanism depends on the integrity of the navicular bone itself and its normal attachment to the ligaments between the lunate and the triquetrum. When the navicular bone is fractured, its proximal broken end is rotated dorsally with the lunate and triquetrum, which can cause instability of the dorsal insertion, whereas the distal end is palmar flexed, causing shortening of the navicular bone and a hunchback deformity. In the case of navicular-lunar separation, the navicular-lunar ligament is ruptured, and the proximal pole of the navicular bone is located between the radius and cephalad in a changed position, causing palmar flexion of the navicular bone and dorsal rotation of the lunate and deltoid. The proximal row of carpal bones are in motion with each other during flexion and extension of the hand and radial and ulnar deviation, but it is not a fixed functional whole. The basis for this interaction between the proximal row of carpal bones lies in the unique geometry of the individual carpal bones and the integrity of the intercarpal ligaments (Kauer 1974, deLange 1985, 1990, Kauer 1992), with the greatest movement between the navicular lunate and to a large extent the integrity of the intercarpal ligaments determining the behavior of the navicular lunate and the lunate-triquetral intercarpal movement being smaller, with only a 1-2 mm of distal and proximal direction movement, radial deviation-distal, ulnar deviation-return to proximal, the lunar triangle articular surface morphology and ligaments together form a self-locking system. The movements of each carpal bone are again interdependent. Physiologically, the distal carpal bones act as a solid unit, whereas the proximal carpal bones exhibit interdependent intercarpal motion – determined by the geometry of the carpal bones and their unique ligaments. The kinematic behavior of the proximal carpal bones depends on the position of the distal carpal bones and the intermovement of the proximal carpal bones. In the central chain, the lunate has a unique kinematic state, and at the level of the radiocarpal joint, with radial deviation and metacarpal flexion – the lunate is rotated metacarpally (with respect to the radius), and with ulnar deviation and dorsal extension – the lunate is rotated dorsally (with respect to the radius). It has been noted (Sarrafian, 1977) that in extreme palmar flexion of the wrist, 40% of the motion occurs at the radial carpal joint and 60% at the midcarpal joint, and in extreme dorsiflexion, the radial carpal joint motion accounts for 66.5% of the motion, and at the midcarpal joint it is 33.5%. These studies concluded that the navicular bone functioned with the proximal row of carpal bones during palmar flexion and with the distal row of carpal bones during dorsal extension. Although the above theories on wrist kinematics are not necessarily perfect, and some aspects are even contradictory, understanding them can still help us to recognize the multidimensionality of wrist motion and point out the direction for future research. Fourth, the stress distribution of the carpal bone The stress on the carpal bone is affected by the direction of the stress, the point of action, the mode of action, and the geometry and orientation of the intercarpal joint, radial-ulnar carpal joint surface. When the mid-carpal joint is in neutral position, 50%-61% of the stresses carried by the distal carpal bones are transmitted to the navicular and lunate bones through the skull, 17%-30% to the STT joints, and 15%-21% to the HT joints. In the neutral position of the radial-ulnar carpal joint, 50%-56% of the stress was distributed in the radial navicular joint, 29%-35% in the radial lunate joint, and 10%-21% in the ulnar deltoid joint. The maximum peak pressure ratio between the navicular fossa and lunate fossa of the distal radius is 1.5:1, and the stress and maximum peak pressure vary with the position of the wrist joint, with the radial deviation – navicular fossa ↑, and the ulnar deviation – lunate fossa ↑. V. Stabilizing mechanism of the carpal bones Stabilizing mechanism of the mid-carpal joint: When axial stress is applied to the distal carpal bones, the distal carpal bones move proximally as a functional whole, with mild dorsiflexion relative to the proximal carpal bones, generating stress → proximal carpal bones, resulting in palmar flexion and rotation of the navicular bone (under control of the navicular size polypoidal ligament and the metacarpal navicular capitellar ligament), and when the navicular- lunate ligament is intact (especially the dorsal part of the navicular ligament), the moment of navicular flexion is transmitted to the lunate, and the head of the navicular bone is directed towards the lunate, and the head of the navicular bone is directed towards the lunate. Relative to the lunate, the skull moves palmarly, reinforcing the tendency of the lunate to flex. Two kinds of motion behaviors occur in the triangular bone, the palmar flexion moment of the lunate bone conducts → the triangular bone, causing it to have a tendency to palmar flexion, and the dorsal extension moment of the skull and hook bone conducts → the triangular bone, causing it to have a tendency to dorsal extension, with the former dominating. In conclusion, under axial stress, the proximal row of carpal bones maintains the same movement or rotation pattern-rotation toward palmar flexion, radial deviation, and mild posterior rotation. If the ligaments associated with the midcarpal joint are intact, a stabilizing mechanism exists in the midcarpal joint, and the rotational dorsiflexion of the distal carpal bones constrains the palmar flexion rotation of the proximal carpal bones. Destruction of the ligamentous structure will result in the formation of carpal instability of the proximal carpal bones, which is characterized by radial deviation, metacarpal flexion, and semidislocation of the metacarpal direction of the skull. Stabilizing Mechanisms for Proximal Row Carpal Bones: Under axial stresses, the proximal row of carpal bones have two opposing kinematical behaviors: the one induced by the navicular bone The other is triggered by the distal carpal bone, which is transmitted to the triangular bone through the midcarpal joint ligament, resulting in a tendency of dorsal extension of the proximal carpal bone. These two opposite mechanisms produce corresponding moments in the navicular and triquetral joints, and when the ligaments are intact, they can constrain each other to strengthen and maintain the stability of the joints; when the navicular ligaments are injured, the navicular bone rotates further into palmar flexion and anterior rotation and the lunate bone rotates further into dorsiflexion; and when the lunotriquetral ligaments are injured, the lunate bone collapses into palmar flexion together with the navicular bone. Therefore, the integrity of the navicular-lunar and lunotriangular ligaments is important for the stabilization of the interproximal carpal bones. Stabilization mechanism of the radial wrist joint: In the radial wrist joint, due to its anatomical and structural characteristics, the carpal bones under stress have a tendency to slide to the palmar and ulnar sides (as determined by the morphology of the articular surface of the distal radius), the palmar radial lunotriquetral and dorsal radial deltoid ligaments constrain the tendency of the carpal bones to slide ulnarly, and the palmate lip of the articular surface of the distal radius and ulnar carpal ligament complex constrain the tendency of palmar side to slide, and when the above supporting and constraining ligaments are damaged and lax, the carpal bones may move to the palmar-carpal side. When the above supporting and restraining ligaments are damaged or loosened, the carpal bones may be semi-dislocated to the metacarpal-ulnar side or occasionally completely dislocated. There are many common terms or concepts related to carpal instability, and there are many differences among them. The following common terms or concepts can be used for clinical reference. Carpal Instability: Traumatic Carpal Instability: Carpal injury that results in a change or loss of normal anatomical arrangement of the bones of the carpal joint and leads to a change in the normal kinematic behavior of the carpal joint (Dobyns, Linscheid, Kauer). A condition in which one or more of the carpal bones move in an abnormal manner due to bony abnormalities, ligamentous injuries, joint laxity, etc., thereby altering the kinematic behavior of the wrist joint (Ekenstam). It refers to a group of clinical signs characterized by abnormalities in the combined relationship or motion of the bony components of the wrist joint, due to trauma, inflammation, and congenital laxity of the joint ligaments. Pathological mechanisms causing carpal instability: ligament injury, fracture or fracture deformity healing, a combination of the above two causes (Tian Guanglei) Currently, the meaning of instability has been extended to any carpal injury that causes pre-existing instability or potential instability. 2, intermediate or embedded (Intercalated Segment): refers to part or all of the proximal row of the carpal bones, mostly referring to the lunate bone. 3.Intercalated or inlaid dorsal instability (DorsalIntercalatedSegment Instability, abbreviated DISI)): relative to the radius or skull, part or all of the proximal row of carpal bones (mostly referring to the lunate) in a dorsal position. 4. Volar Intercalated Segment Instability (VISI): part or all of the proximal row of carpal bones (multifidus lunate) are in a position of palmar flexion with respect to the radius or skull. 5, Dissociation (Dissociation) and Nondissociation (Nondissociation): refers to the distal or proximal row of carpal bones adjacent to the two carpal bones between the ligament rupture or not. 6. CarpalInstability Nondissociative (CIND): occurs between the distal and proximal rows of carpal bones or between a row of carpal bones and the adjacent transverse osseous system, and the injury occurs to the extrinsic ligaments or the capsular ligaments. Carpal Instability dissociative (CID): It occurs between the carpal bones or between the carpal bones of the same row of carpal bones, and the intrinsic ligaments between the carpal bones are completely or partially ruptured, and the extrinsic ligaments or the joint capsule ligaments can be ruptured in severe cases. 8.Composite Carpal InstabilityCombinedorComplex(CIC)：CIND and CID exist at the same time. 9.Midcarpal Instability（MI）: instability caused by injury at the level of the midcarpal joint. 10.Ulnar Translation or Translocation (UT): the bones of the wrist as a whole are displaced to the ulnar side; or the position of the navicular bone remains unchanged while the other bones of the wrist are displaced to the ulnar side, and an abnormal gap is formed between the navicular and lunate bones. 11, Dorsal Translation (Dorsal Translation or Translocation, abbreviated DT): relative radial carpal bones to the dorsal displacement. 12.Palmar Translation or Translocation (abbreviated PT): the opposite of DT. 13, Dynamic Instability (Dynamic Instability): conventional X-ray without abnormal findings, the application of external forces or through special manipulation or inspection can make the carpal bone sort of abnormal. 14, Static Instability: routine X-ray can show abnormal carpal bone sorting. 15, Medial Instability (Medial Instability): the medial carpal bone column is unstable. Lateral Instability: Instability of the lateral carpal column. 17, Proximal Instability (Proximal Instability): proximal Dynamic carpal bone column instability, including the radial wrist joint and the middle carpal joint instability. 18, Dorsal Subdislocation: relative to the radius, the carpal bones are displaced to the dorsal side. 19, Metacarpal subdislocation (Volar Subdislocation): relative to the radius, the carpal bones are displaced to the metacarpal side. 20.Adaptive Carpal or Pseudo Carpal Instability (AdaptiveCarpus or Pseudo Carpal Instability): the ligament itself is intact, due to the radius or navicular bone fracture deformity, Keinbock’s disease and other reasons for the adaptive arrangement of carpal bone structure is abnormal, leading to instability occurs. VII.Classification of carpal instability There is no classification system for carpal instability that can be widely accepted, but certain objective indicators, such as injury time, etiology, location, constancy, direction and pattern, can be used as criteria for classification. Carpal instability is acute if the time of injury is within 2 weeks, subacute if within 2-4 weeks, and chronic if more than 4 weeks. The time of injury is an important indicator of the outcome of treatment of ligamentous injuries of the wrist, i.e., the more timely the treatment, the greater the chance of healing of the injured ligament, and, of course, the more satisfactory the final outcome, and conversely, the outcome is still quite uncertain, even with the many ligament reconstructions and other remedial treatments currently available. Trauma and rheumatoid arthritis are the most common causes of ligamentous injuries of the wrist joint, but it is also common to see people with obvious signs of joint instability but no symptoms or no effect on their daily life, which are mostly seen in young women or adolescents, and may be related to congenital laxity of their ligaments or ligamentous laxity is just a temporary process of their physiological development. Clinical experience at home and abroad has shown that navicular-lunate interosseous separation is the most common type of injury, followed by lunate-triangular interosseous separation, which is much less common in our clinic than in foreign countries. The reason for this may be due to the fact that the conventional radiograph is not as easy to recognize as the navicular-lunate interosseous separation, and at the same time the use of arthroscopy of the wrist is not very popular. Static and dynamic carpal instability is often a manifestation of the degree of ligamentous injury, which requires some special means of examination or arthroscopy to make a judgment, especially the latter standard X-ray film usually has no abnormality to be seen, and for those who do not have clinical experience, it is very likely to cause the possibility of omission. Due to the anatomical shape of the lunate itself, its bony arrangement with the adjacent carpal bones or radial-ulnar bones, and the uniqueness of its ligamentous connections, the role it plays in maintaining the stability of the carpal joint is extremely important, and it is believed that the lunate is an important anatomical and imaging landmark for the study of physiological and pathophysiological movements of the carpal joint, and that it produces an intermediate or nested dorsal instability according to the direction of the displacement of the lunate (Dorsal IntercalatedSegmentInstability (abbreviated DISI) and VolarIntercalatedSegment Instability (abbreviated VISI). Carpal instability is categorized into four patterns, CarpalInstability Nondissociative (abbreviated CIND), CarpalInstability dissociative (abbreviated CID), Composite Carpal Instability ( CarpalInstabilityCombinedor Complex, abbreviated CIC) and adaptive carpal or instability. The concept of axial instability mainly refers to the condition where the separation between the base of the metacarpal bone and the carpal bone exists simultaneously. A perfect classification system of carpal instability, in addition to covering as comprehensively as possible the indicators related to it, should also meet the following conditions: firstly, it is simple, easy to memorize and easy to use clinically, secondly, it can accurately and directly guide the diagnosis and treatment, and thirdly, it is conducive to the statistics and summarization of clinical cases. At present, there are many classification systems for wrist joint instability, and the definitions of each are quite different from each other, which is very difficult to understand. The classification is based on clinical manifestations, radiologic changes, anatomical abnormalities, etc. Different classification systems focus on different aspects, and some classifications combine all of the above changes. The Mayo classification system is a very detailed and comprehensive classification system, but it is a bit complicated, inconvenient for clinical application and difficult to memorize. Its most important feature is that according to the degree of ligament damage, wrist instability is divided into separated, non-separated, mixed and adaptive carpal bones (carpal instability), according to which the nature, degree and extent of carpal instability and carpal ligament damage can be known with relative clarity. The Taleisnik classification of carpal instability into medial, lateral, and proximal instability based on the site of the instability is relatively concise and clear, and is easy to remember and understand. In particular, the nature of carpal instability is described and in this classification it is divided into dynamic and static types. The concepts of dynamic and static instability can enable clinicians to accurately and clearly determine the nature of carpal instability, which makes up for the lack of previous understanding of dynamic instability and makes the connotation of carpal instability more complete. The author believes that this is a concise, easy to understand and memorize classification method, which is suitable for clinical application. Taleisnik typing Static type Dynamic type Lateral instability Medial instability Proximal instability 1. navicular polygonal interosseous instability 1. lunotriquetral interosseous separation (static VISI) 1. radial carpal instability 2. navicular cephalic interosseous separation 2. triquetral hook interosseous separation ulnar displacement 3. navicular lunotriquetral interosseous separation a. Dynamic VISI Dorsal subluxation (DISI with SLD) b. Without SLD DISI metacarpal subluxation 2. midcarpal joint instability (secondary to DISI without SLD) Taleisnik typing Static type Dynamic type Lateral instability Medial instability Proximal instability 1. navicular polygonal interosseous instability 1. lunate-triangular interosseous separation (static VISI) 1. radial carpal instability 2. navicular cephalocaudal interosseous separation 2. triangular hook interosseous separation Ulnar displacement 3. naviculolunate interosseous separation a. Dynamic VISI dorsal subluxation (DISI with SLD) b. DISI palmar subluxation without SLD 2. Midcarpal joint instability (secondary to DISI without SLD) The McMurtry Classification is a more complex and detailed one based on a series of injuries to the periosteum.The Viegas Classification focuses more on the periosteum as the typing of the instability. The Viegas classification is more focused on the classification of periprosthetic instability as the basis for classification into radial and ulnar periprosthetic instability. There are other classification methods that are also used in clinical practice. Regardless of the method, if it can also indicate the location of the injury or lesion and the nature of the lesion, which can help clinicians to choose the accurate treatment method and evaluate the treatment effect, this classification is worthy of respect.