Wrist Instabilities

Shrikant J. Chinchalkar and Joey G. Pipicelli

Introduction

The wrist is an intricate joint with complex motion and function and is comprised of several articulations. These articulations are formed by various anatomical structures with varying degrees of curvatures and congruencies supported by the ligamentous elements, controlled by musculotendinous units, and based on precise proprioceptive input from various ligaments. The meticulous normal functioning of the hand is dictated by the stability and mobility of the carpus, allowing the hand to grasp objects in a variety of wrist positions.

Carpal dislocations and instabilities are common injuries, especially in young adults. Most carpal disruptions are caused by trauma; however, conditions such as congenital laxity, infection, inflammatory processes (rheumatoid arthritis), or congenital defects can also be the culprit. Carpal dislocation and instability injury patterns can be easily misdiagnosed, because an exact diagnosis is often difficult to establish. If such injuries are not correctly diagnosed, this can eventually lead to premature degeneration and arthrosis at radiocarpal and midcarpal joints due to altered carpal kinematics.

Carpal instability is defined as dislocation or loss of contact between bones of the distal carpal row over the proximal carpal row in relation to the radioulnar joint. The loss of contact is either static or dynamic, causing a decreased ability to transfer loads across the wrist during motion or function. Common symptoms reported by patients include pain, sudden loss of motion control, and at times clunking associated with pain and weakness. Untimely identification and inadequate management of carpal instabilities will cause abnormal intercarpal and radiocarpal loads, ultimately leading to degeneration at the articular surfaces. In order to understand carpal instability, an understanding of the anatomy of the wrist joint and the kinematics of the carpal bones is imperative.

The wrist consists of the distal radius and ulna forming the distal radioulnar joint. The distal radius is typically tilted in anterior/posterior (A/P) plane by an average of 11° (Fig. 26-1, A) and radioulnar plane by 23° (see Fig. 26-1, B). The distal radius is composed of two fossae—a rectangular and shallow fossa for the articulation of lunate, and a deep triangular fossa for the scaphoid (Fig. 26-2). The distal surface of the ulna is covered by the triangular fibrocartilage complex (TFCC). The proximal carpal row is formed by the scaphoid, lunate, and triquetrum, whereas the distal carpal row is formed by the trapezium, trapezoid, capitate, and hamate. The joint formed by both these rows is the midcarpal joint. The midcarpal joint has three articulations: lateral, central, and medial. The lateral segment of the midcarpal joint is formed by the convexity of the distal pole of the scaphoid articulating with the concavity formed by the trapezium, trapezoid, and lateral aspect of the capitate. The central portion of the joint is formed by the proximal concavity of the scaphoid and lunate and distally by the convexity of the head of the capitate and the proximal pole of the hamate representing a “ball and socket” articulation. Medially the joint is formed by the articulation of the hamate and triquetrum. The midcarpal joint is highly synovial, thus allowing for maximal motion in all the planes. The scaphoid bridges both proximal and distal carpal rows. The pisiform, a sesamoid bone, is in the substance of the flexor carpi ulnaris (FCU) tendon, which articulates with the triquetrum. The proximal carpal row has been termed as an intercalated segment between the distal carpal row and the radius. The bones of the proximal carpal row move directly in response to the muscular force regulated by the ligaments that connect to the forearm and the distal carpal rows.^1–4

FIGURE 26-1 A, The distal radius is typically tilted an average of 11 degrees in the anterior-posterior plane. B, The distal radius is tilted an average of 23 degrees in the radial-ulnar plane. This is called radial inclination.

Ligamentous Anatomy

The ligamentous structures are divided into extrinsic, intrinsic, palmar, and dorsal.⁵ The palmar extrinsic ligaments arise from the distal radius and ulna, and they connect to proximal and distal carpal rows. These ligaments are labeled in accordance with their length and insertion.

Palmar Ligaments

Clinical Pearl

The palmar extrinsic ligaments are stronger than the dorsal extrinsic ligaments and are considered the main stabilizers of the radiocarpal joints.⁵

The radioscaphocapitate (RSC) is the radial most ligament originating from the radial styloid, and it traverses across the distal pole of the scaphoid connecting to the waist of the capitate. This ligament blends into the ulnocapitate (UC) ligament arising from the ulnar side. The RSC ligament is a primary radial stabilizer of the wrist and resists ulnar translation of the carpus over the radius. Lateral to the RSC ligament, the radioscapholunate (RSL) ligament provides neurovascular supply to the carpal bones and has no contribution to carpal stability. Lateral to the RSL ligament, the long radiolunate (LRL) and short radiolunate (SRL) ligaments offer primary resistance to lunate displacement, thereby preventing perilunate dislocation.⁶

On the ulnar side, the palmar ligaments, such as the ulnotriquetral (UT) and ulnolunate ligaments, arise from the TFCC and distal ulna. The medial most ligament, which arises from ulna, is called the UC ligament. As previously mentioned, this ligament blends in with the RSC ligament forming an acute structure. These ligaments connect the ulna to the carpus.

Palmar Intrinsic Ligaments

The palmar intrinsic ligaments are named based on their connection between the carpal bones. The proximal carpal bones are stabilized by the scapholunate (SL) ligament on the radial side and the lunotriquetral (LT) ligament on the ulnar side. The SL and LT ligaments have certain characteristics. The SL ligament has three distinct components: palmar, dorsal, and proximal. The dorsal SL ligament is the toughest portion of the ligaments and is responsible for preventing excessive flexion and rotation of the scaphoid, whereas the LT ligament is toughest on the volar side, which prevents ulnar translation of the lunate. Two deltoid or arcuate intrinsic ligaments consist of scaphocapitate and triquetrocapitate ligaments. These ligaments serve as the stabilizer of the midcarpal joint. Trapezio-trapezoid, trapezio-capitate, and capito-hamate ligaments connect the bones of the distal carpal row.

Clinical Pearl

The space in-between both the proximal and distal carpal rows is termed the space of Poirier and is where most common patterns of carpal collapse and instability occur.

Dorsal Ligaments

The dorsal intrinsic wrist ligaments are intracapsular and are not as well-defined and strong as the volar intrinsic ligaments (Fig. 26-3, A). The dorsal extrinsic ligaments of the wrist consist of dorsal radiocarpal (DRC) and dorsal intercarpal (DIC) ligaments (see Fig. 26-3, B). The DRC originates from the dorsal distal radius at Lister’s tubercle crossing, obliquely inserting on the triquetrum. The DRC ligaments prevent ulnar translation of the carpus. The DIC ligament originates from the triquetrum and extends towards the distal pole of the scaphoid and trapezoid where it inserts. This ligament provides stability to the midcarpal joint preventing dorsal dislocation of the capitate from the SL interval.

FIGURE 26-3 A, The dorsal intrinsic wrist ligaments are intracapsular and are not as well defined and strong as the volar intrinsic ligaments. B, The dorsal extrinsic ligaments of the wrist consist of dorsal radiocarpal (DRC) and dorsal intercarpal (DIC) ligaments.

Retinacular Ligaments and Tendons Responsible for Wrist Motion

Other attachments to the carpus consist of distinct fascial layers of extensor and flexor retinaculum. The extensor retinaculum consists of two layers: infratendinous and supratendinous. The extensor retinaculum inserts on the palmar margin of the distal radius and ulnarly on the pisiform on the volar aspect. In between two layers of extensor retinaculum, vertical septii divides the extensor tendons into six different compartments. The primary extensors of the wrist include the extensor carpi radialis brevis (ECRB) and extensor carpi radialis longus (ECRL) on the radial side and extensor carpi ulnaris (ECU) on the ulnar side. The digital and thumb extensor tendons also supplement wrist extensor force to some degree.

On the palmar side, the flexor retinaculum attaches to the hook of the hamate and pisiform, and on the radial side, it inserts on the scaphoid tubercle and the tuberosity of trapezium. The flexor retinaculum forms a carpal canal that contains the median nerve and nine flexor tendons shared by the fingers and thumb. The primary wrist flexors consist of the flexor carpi radialis (FCR) and FCU. The FCR inserts on the base of second metacarpal, whereas the FCU inserts on the pisiform with extension in a form of ligaments connecting to the hamate (pisohamate ligament) and the base of the fifth metacarpal (pisometacarpal ligament). Other than the FCU, no other tendinous insertions exist on the carpus, except for the abductor pollicis longus (APL) inserting on the trapezoid, trapezium, and distal pole of the scaphoid as an anatomical variation.

Normal Kinematics of the Wrist Joint

Understanding the complexities of carpal motion is based on various evolutionary studies that identified the instability patterns of the wrist. Navarro ⁷ originally proposed the column theory. He suggested that the carpus was made up of three columns: central, radial, and ulnar. This column theory was later modified by Taleisnik.⁵ Other studies including work by Lichtman, et al.² identified the four-unit concept, whereas Linscheid, et al.¹ introduced a slider crank mechanism of the scaphoid. Linscheid, et al.¹ also identified that regardless of the previously published studies illustrating the normal kinematics, the scaphoid maintains an average of 47° of flexion orientation in relation to the lunate and radius on lateral radiograph. The SL ligament plays an important role in neutralizing the flexion tendency of the scaphoid under physiologic loads. Gillula and Weeks⁸ identified that there is a distinct parallelism between the curvatures of the proximal and distal carpal rows on A/P radiograph. The proximal carpal row’s behavior during flexion/extension or radio/ulnar motion is based on its central placement between two rigid structures (that is, distal radius proximally and stable distal carpal row distally).

The motion of the carpal bones during flexion/extension and radial/ulnar deviation of the wrist is extremely complex. The motion of the proximal carpal row is dependent on the compressive loads placed by the distal carpal row. The musculotendinous units inserting distal to the distal carpal row produce this physiologic load on the carpus. Having normal anatomic relationship of the proximal carpal row structures along with the radius is critical for normal functioning of the wrist joint to occur.⁹

Flexion/Extension Motion

During extension of the wrist, the lunate extends and translates palmarly, whereas the capitate rotates dorsally.¹⁰ The palmar radiolunate ligament prevents excessive rotation of the lunate, preventing dorsal intercalated segmental instability (DISI). When the wrist is flexed, the lunate translates dorsally and the capitate rotates palmarly. The DRC and DIC ligaments prevent excessive rotation of the lunate, preventing volar intercalated segmental instability (VISI).

Radioulnar Motion

Radioulnar motion of the wrist is more complex than the flexion/extension arc of motion. The radioulnar motion of the wrist influences both of the carpal rows to move in different directions. The distal carpal row rotates in a radial direction, whereas the proximal carpal row slides in an ulnar direction when radial deviation is performed; a reversal mechanism occurs when the wrist is brought into an ulnar deviation posture. These changes occurring in both the carpal rows are influenced by the geometry of the carpus, ligamentous constraints offered by the extrinsic and intrinsic ligaments of the wrist, and the muscles of the wrist acting through the distal carpal row.

Upon radial deviation of the wrist, the distal pole of the scaphoid is compressed between the radial styloid proximally and the trapezium-trapezoid distally, forcing the distal pole of scaphoid to flex in almost perpendicular direction to the radius. As the scaphoid flexes, the entire proximal carpal row also assumes a flexed position. The intact SL and LT ligaments cause the entire proximal carpal row to follow the scaphoid’s tendency towards flexion. During radial deviation the ulnar ligaments (such as, ulnocarpal, ulnar lunate, and UT) stretch, whereas the ligaments on the radial side become lax. Tensioning of the UT ligament influences the triquetrum, causing it to slide or disengage off the waist of hamate. Besides these changes, the motion of the wrist in a radial direction produces a translatory effect on the proximal carpal row, which then slides in an ulnar direction. A synchronous motion that occurs with radial deviation involves execution of the proximal row in pronation and flexion, whereas the distal carpal row moves in the opposite direction of supination and extension.

As the wrist is moved in ulnar deviation, a compressive force is produced by the hamate over the triquetrum, which forces it into extension, and subsequently the entire proximal carpal row is brought into extension. The entire proximal carpal row slides radially because of tensioning of the RSC, LRL, and SRL ligaments. In addition, as the extension of the proximal carpal row increases with the increment of the deviation, the scaphoid is pulled into extension with lunate and triquetrum. Besides this, the proximal row executes supination and extension, whereas the distal row moves in pronation and flexion.

Motion of the Carpus during Gripping

Studies on load distribution during gripping activities have demonstrated that 80% of the load is transmitted on the radiocarpal joint and 20% on the ulnocarpal region, especially when the radioulnar relationship is in neutral ulnar variance.¹¹ Out of the 80% radial load, 60% of the load transmission is on the scaphoid, whereas 40% of the load is transmitted on lunate. The load variation changes proportionately, either negative or positive, if ulnar variance is present. In neutral ulnar variance, the forces produced by the flexors and extensors are transmitted from the digits to the distal carpal row upon gripping and then through the proximal pole of capitate to the SL interval. A radiologic investigation using a classic stress test by making a fist is recommended to diagnose partial SL ligament tears, especially in the carpal instability non-dissociative (CIND) category of carpal instability. (This will be discussed later in the chapter.) The carpal motion studies during gripping have shown that the scaphoid demonstrates a tendency to rotate in flexion and pronation; the lunate rotates dorsally, whereas the triquetrum rotates in flexion. The rotatory tendency of the carpus during gripping activities suggest that the proximal carpal row (that is, the intercalary segment) moves together because of the intact SL and LT ligaments. In addition, the dislocation of the carpus is prevented by the palmar intrinsic, as well as the dorsal and palmar extrinsic ligaments.

Dart Throwing Motion

Other physiologic motions of the wrist that are commonly used in activities of daily living (ADLs) involve motion in an oblique plane. The majority of ADLs, such as combing hair or hammering a nail, are performed in a distinct manner. The motion of the wrist involves a combination of wrist extension in radial deviation and flexion with ulnar deviation. This motion has been coined as a dart throwing motion (DTM).¹² The International Federation of Societies of the Hand (IFSSH) Committee¹³ recommends the motion taking place at the wrist joint in the so-called DTM be called radial extension and ulnar flexion. In vivo investigation of length changes in carpal ligaments during DTM demonstrates that the palmar radiocarpal ligaments’ length decreased significantly, whereas the DIC ligaments inserting on the trapezoid lengthened, and the UL and DIC inserting on the scaphoid remained shortest in neutral wrist position. These findings also suggest that DTM does not cause greater loads on the carpal ligaments. In addition, the arcuate ligament (that is, RSC and UC ligaments) resisted excessive motion of the capitate contributing to the midcarpal joint stability.¹⁴ From a carpal motion point of view, the DTM, revealed minimal scaphoid and lunate motion when compared to pure radioulnar or flexion extension arc of motion.^15–17 The muscles that produce DTM are the FCU and the ECU and ECRB and ECRL. DTM will be discussed further later in this chapter.

Muscular Contributions to the Motion of the Wrist and Their Effect on Carpal Stabilization

The motion of the wrist joint in flexion, extension, and radioulnar direction is dependent on various muscular contractions. The palmaris longus, FCR, and FCU produce flexion of the wrist. The digital flexors also contribute secondarily to the flexion of the wrist joint. The ECRB, ECRL, and ECU are the prime extensors of the wrist. Additionally, the digital extensors also contribute secondarily to the extension action at the wrist. Radial deviation is primarily dependent on the action of FCR and ERCL; in addition APL, because of its radial orientation, contributes to radial deviation of the wrist joint. Motion in ulnar deviation is a result of ECU and FCU contraction. The kinematics of the carpus in flexion/extension, as well as the radioulnar arc, were described in the previous section. Based on the kinematics, it is apparent that the deforming forces are produced at the distal pole of the scaphoid, resulting in the intercalary motion of the proximal carpal row. Cadveric studies by Garcia-Elias ¹⁸ and Hagert, Forsegren, & Ljung¹⁹ on the effect on carpal alignment during loading of the muscles have shown that ECU contraction stresses the SL ligament, whereas FCU, FCR, and APL activity reduces the load on the injured SL ligament. In addition, Garcia-Elias¹⁸ identified that FCU and hypothenar muscle contraction produced dorsally directed forces on the triquetrun through the pisiform, which stabilized midcarpal as well as LT joint instability. Based on these cadaveric studies, the authors recommend that the proprioceptive training of these muscles would be beneficial in SL, LT, and midcarpal instabilities. These suggestions are based on cadaveric experimentations, and implementation in clinical situations needs further investigation.

Proprioceptive Input during Motion of the Wrist

As mentioned previously, the motion of the wrist is highly complex.

Clinical Pearl

In order to move the wrist in various planes, either with or without loading, the wrist joint must maintain entire stability between the radiocarpal and intercarpal joints.

This maintenance of stability during motion is provided by several mechanoreceptors and proprioceptors embedded in the joint capsule and ligaments. These structures are continuously sending feedback to the central nervous system (CNS) about the position of the joint and the speed of motion being performed. In addition, the information regarding pressure, torsion, and sensation of the pain sent to the CNS regulates muscular contraction to maintain the joint stability. A concentration of nerve endings responsible for sending information to the CNS have been found in the dorsal radio carpal ligaments, RSL ligaments, and SL and LT ligaments. The RSL ligament was identified to be responsible for monitoring the SL relationship. The SL and LT ligaments provide continuous sensory feedback during motion of the wrist joint. Upon electrical stimulation of the SL ligament, recruitment of FCR and FCU was recorded with reciprocal activation of ECU and ECRB, suggesting that these muscles guided prevention of instability of the joint. Thus, proprioceptive reeducation may add a benefit in treating ligamentous injuries of the wrist joint.

Carpal Instability Classification

Attempts to simplify our understanding of carpal motion have led to the development of multiple classification systems of carpal instability.5,20–22 Perhaps the most widely-adopted classification system is the Mayo Classification,²³ which classifies carpal instability into four major categories:

• Carpal instability dissociative (CID)

• Carpal instability non-dissociative (CIND)

• Carpal instability complex (CIC)

• Carpal instability adaptive (CIA)

Rehabilitation of Carpal Instabilities: Current Practice

The literature describing the rehabilitation of carpal instability is limited. Most rehabilitation programs described are based on author preference and experience.28–32 These rehabilitation programs are based on sound clinical reasoning; however, they have not been established as best practice, because clinical research studies are lacking. As such, carpal instability rehabilitation should be based on the stages of tissue healing when making clinical decisions regarding the length of time of immobilization, initiation of controlled protected motion, gradual tissue loading, and resumption of unrestricted hand use during functional activity, sport-, and work-related tasks. General rehabilitation following operative or non-operative management of wrist ligament injury should include the following:

• Edema and pain control

• Through traditional means, including pharmacology, cryotherapy, compression, elevation, and cast/orthotic application

• Maintenance of range of motion (ROM) to the uninvolved joints

• Initiation of controlled, protected mobilization to the involved structures based on stages of tissue healing, observed intra-operative tension to repaired structures, and symptomology of the patient

• Avoidance of exercise or activity that may compromise tissue healing or place undue load to the healing/repaired structures

• Avoidance of generic wrist ROM and strengthening exercises

• Avoidance of aggressive ROM and excessive active ROM exercises

• Overall achievement of a stable wrist with functional ROM; functional ROM should be based on the work of Palmer and colleagues,¹³ which found that functional wrist ROM is between 5° of wrist flexion to 30° of extension, 10° of radial deviation, and 15° of ulnar deviation

Innovative and Emerging Approaches to Carpal Instability Rehabilitation

New lines of research investigation have elucidated the role of proprioception in stabilization of the wrist. This follows previous investigations of the role of proprioception in the stabilization of other articulations, such as the shoulder, ankle, and knee. However, for therapists to understand these emerging ideas, we must first have a sound foundation of the neuromuscular rehabilitation concepts.

The term proprioception has been used since the early twentieth century to describe our body’s regulation of posture, balance, joint stability, and audiovisual-motor coordination.³³ Our body maintains appropriate proprioceptive feedback through homeostasis. Homeostasis is defined as a dynamic process by which an organism maintains and controls its internal environment despite disturbances from external forces.³⁴ The body is composed of many systems that operate automatically and subconsciously to maintain a homeostatic state.³⁵

The term sensorimotor function was adopted by the participants of the 1997 Foundation of Sports Medicine Education and Research workshop in order to describe the sensory, motor, and central integration and processing components involved with maintaining joint homeostasis during movement.³⁶ This was an attempt to recognize the portion of proprioceptive research dealing with only joint control.

The process of maintaining joint control and stability is accomplished through the relationship between the static and dynamic joint stabilizers. Ligaments, joint capsule, cartilage, and joint articulation bony geometry comprise the static stabilizers.37–39 Dynamic contributions to joint stability arise from the skeletal muscles that cross the joint structures. If there is a disruption in the static stabilizers of a joint, the dynamic joint stabilizers must work harder and become smarter and stronger in order to provide enhanced joint stability. However, in order for this to occur we must optimize ligamentomuscular reflexes.

Ligamentous and Muscular Reflexes, Proprioception, and the Wrist

Clinical Pearl

Intact wrist ligaments are responsible for wrist stability. However, these ligaments also provide the brain with important sensory input, which enhances the dynamic stability of this complex structure.20,40–43

The sensory input provided by the intact wrist ligaments is delivered to the brain through afferent pathways. The sensory end organs that provide this information are the joint mechanoreceptors, because they react to joint pressure, motion, and velocity. The brain then interprets these afferent impulses as joint position sense (JPS), kinesthesia, sense of resistance, motion threshold, and velocity.

The existence of mechanoreceptors in the ligaments of the wrist was first identified by Petrie, et al. in 1997.⁴⁴ Since this time, there have been numerous studies on the innervation of the various wrist ligaments.^{20,40,41,45–47} These studies found that nerve endings in the various wrist ligaments are predominately located close to the ligament insertion into bone. This ensures firing of the mechanoreceptors only at the extremes of joint motion as the collagen fibers within the ligament have higher stiffness at their insertion into bone.⁴⁸ Mechanoreceptors are also found in the DRC and DIC ligaments in the pliant epifascicular regions where they can be readily stimulated and able to provide information throughout the range of wrist motions.^20,42 Interestingly, the ligaments of the radial and volar wrist ligaments have little to no innervation. However, the dorsal and triquetral wrist ligaments (DRC, DIR, dorsal SL, palmar LT, and triquetrocapitate/hamate ligaments) are the most densely innervated.^40,49 What does this mean? The dense mechanically important ligaments that are designed to withstand axial loads are located in the radial column of the wrist. The sensory important ligaments are the dorsal wrist ligaments and ligaments emerging from the triquetrum and should be regarded as key elements in the generation of proprioceptive information required for adequate neuromuscular wrist control (Fig. 26-6).⁵⁰

FIGURE 26-6 Mechanoreceptor and nerve distribution in the wrist ligaments including the Triangular Fibro-cartiliage Complex. Ligaments: dorsal radiocarpal (1), dorsal intercarpal (2), scaphotriquetral (3), scapholunate interosseous (4), ulnar collateral (5), dorsal radioulnar (6), volar radioulnar (7), triquetrohamate (8), triquetrocapitate (9), palmar lunotriquetral (10), ulnolunate (11), short radiolunate (12), long radiolunate (13), radioscaphocapitate (14), radioscaphoid (15), scaphocapitate (16), scaphotrapeziotrapezoid (17). (Courtesy Hagert E, Wrist Ligaments—Innervation Patterns and Ligamento-Muscular Reflexes, Karolinska Institute, 2008.)

Dart Throwing Motion

DTM refers to the motion pattern commonly used during ADLs and functional tasks. Palmer and colleagues ¹³ found that most tasks are performed in a plane from 40° of wrist extension and 20° radial deviation to 0° of flexion and 20° of ulnar deviation. Biomechanical studies of this motion pattern demonstrate that radiocarpal motion is minimized while most of the motion is occurring at the midcarpal joint.^51–53 The relationship this movement pattern has on tension placed to the scapholunate interosseous ligament (SLIL) has also been studied. The results show that the DTM pattern of the wrist produces minimal elongation and thus minimal tension to the volar and dorsal SLIL.^54,55 The clinical implications to hand therapy rehabilitation are that practice-guidelines can be developed implementing early-controlled motion utilizing the DTM pattern following partial SLIL injuries, SL repairs, or potentially other reconstructive procedures. Orthotic application can be utilized to ensure that wrist motion is within the arc of the DTM pattern of movement (Fig. 26-7). Caution must be used in implementing this type of controlled mobilization pattern following partial SLIL injuries and surgical procedures because no studies have determined the optimal time to introduce this pattern of movement following injury or surgery. It is also unknown how long to restrict motion along the DTM path following injury.

FIGURE 26-7 Custom made dart throw’s motion orthosis. A, Demonstrating radial deviation with slight extension. B, Demonstrating ulnar deviation with slight flexion.

Proprioceptive Reeducation to the Wrist

Ligamentous insufficiency within the wrist may distort proprioceptive responses altering the normal reflex mechanism. This has an effect on dynamic joint stability.⁵⁶ Although proprioceptive reeducation is a relatively new rehabilitation concept applied to wrist instability, it is a well-established part of the treatment of the unstable shoulder, knee, and ankle joint.^57–62

Hagert ⁴⁹ proposed a proprioceptive rehabilitation program for to the unstable wrist joint. The foundation of proprioceptive reeducation is based on identifying muscles that serve a protective function for the specific ligament deficiency and training those muscles to respond more efficiently to prevent injury. Hagert⁴⁹ suggests that the three major proprioceptive senses that have therapeutic implications include kinesthesia, JPS, and neuromuscular rehabilitation.

Kinesthesia

Kinesthesia is the ability to sense motion of a joint or limb. This sense is primarily influenced by muscle spindles and secondarily influenced by skin receptors and joint receptors.63–68 In clinical practice, kinesthesia is measured as the smallest change in joint angle required to elicit conscious awareness of joint motion.^48,69 The common terminology used in proprioception training is “threshold to detection of passive movement.”⁴⁹ It has been suggested that the joint be placed at a certain angle and then slowly moved passively at a speed of 0.5° to 2° per second until the patient signals that limb motion occurs.⁴⁹ The patient should be blinded during initial kinesthesia testing, because limb movement is greatly influenced by visual cues. Also, it may be advisable to use a professional training device (such as, Biometrics Upper Limb Exerciser^∗) in order to precisely control the speed and degree of joint motion.⁴⁹

Joint Position Sense

JPS is a separate entity from kinesthesia.⁷⁰ To describe the differences between JPS and kinesthesia is beyond the scope of this chapter. However, be aware that they differ due to their central processing and interpretation in the brain.⁶⁹

In proprioceptive retraining, JPS is defined as the ability to accurately reproduce a specific joint angle.⁴⁹ This form of retraining can be done with visual cues or blinded, as well as with active muscle contraction or through passive motion. Simply, JPS is when the patient is instructed to move the involved wrist to a predetermined joint angle established by using goniometry. This can be performed actively by the patient or passively by the therapist slowly moving the wrist until the patient identifies when the target position is reached. Hagert⁴⁹ suggests beginning JPS with visual cues progressing to vision occluded exercises as tolerated by the patient. Patient progress and accuracy can easily be recorded simply by using a goniometer