Innovative diagnostic framework for shoulder instability: a narrative review on machine learning-enhanced scapular dyskinesis assessment in sports injuries

Abstract

A common shoulder problem that significantly detracts from patients’ quality of life is shoulder instability (SI). Abnormal scapular positioning and movement are closely associated with rotator cuff injuries and SI, as shown by several studies. The aetiology of scapular dyskinesia (SD) adversely affects shoulder stability and function, including postural abnormalities, musculoskeletal problems, and neurological conditions. Presently, there is a paucity of studies on scapular kinetic alterations in SI rehabilitation. This paper rigorously examines the correlation between SI and scapular kinetic irregularities, as well as the functional alterations of periscapular muscle groups, offering a thorough theoretical foundation and practical guidance for clinicians to enhance their understanding of the disease mechanism and develop a more holistic and effective treatment for patients with SI. We examined the particular manifestations of scapular kinetic disorders in SI patients, evaluated current clinical assessment tools, and explored novel strategies (machine learning, kinetic chain, and scapular biomechanics) for prospective clinical applications. Our objective is to furnish a thorough theoretical foundation and practical guidance for rehabilitating patients with SI, thereby enhancing clinicians’ comprehension of the disease mechanism and enabling the development of more effective rehabilitation programs.

Introduction

The shoulder joint connects the upper extremities to the trunk and has the most excellent range of motion in the human body. The shoulder joint is formed by the glenoid of the scapula and the head of the humerus, stabilized by adjacent muscles and ligaments [1]. The glenoid surface of the scapula constitutes just one-fourth of the surface area of the humeral head, which is hemispherical and exhibits a 30° posterior inclination [2]. The patient’s humeral head cannot maintain a central position during movement owing to static instabilities, such as the disproportionate size of the humeral head’s articular surface relative to the glenoid, and kinetic instabilities, including injuries to the rotator cuff or the long head of the biceps. This leads to symptomatic dislocation or shoulder instability (SI), [3] characterized by joint instability and apprehension, with or without sensory impairment, reduced mobility, and diminished strength [4]. Despite the imperfections in China’s incidence data, SI is a common disorder, representing 45% of all joint dislocations in the United States, with an annual incidence rate of 23.9 cases per 100,000 individuals [5]. The emergence of SI will adversely affect a patient’s quality of life, severely hindering their ability to engage in typical activities and use their shoulders, leading to reduced athletic performance and chronic shoulder pain symptoms [6].

The two most essential treatment modalities for recovering SI are surgical intervention to reestablish stability and rehabilitative therapy to regain stability [7]. Many scholars have discussed the comparative significance of conservative and surgical rehabilitation methods in regaining shoulder stability. Recent investigations have shown that surgical surgery is a more successful therapeutic approach for SI [8]. Nonetheless, conservative rehabilitation treatment for mild shoulder injuries and post-surgical rehabilitation therapy are essential elements of therapeutic practice. Research indicates that rehabilitating the rotator cuff muscles alone has a markedly low success rate for persons with SI accompanied by scapular instability. This may be due to the inadequate rehabilitation of the crucial muscle groups that support the scapula [9]. The recent systematic review [9] has identified that only 12% of SI rehabilitation studies published in the last decade have incorporated scapular kinematic analysis, highlighting a critical gap in understanding dynamic scapular contributions to instability resolution. An increasing amount of evidence indicates that abnormal scapular positioning and motion trajectories are associated with rotator cuff injuries and SI [10, 11]. Scapular dyskinesia (SD) is any scapular posture or movement alteration that may impact shoulder stability and function [12]. A prevailing trend [13, 14] suggests that SI and dyskinesia are increasingly attributed to abnormalities in scapular kinetics rather than a general weakness in scapulo-thoracic muscle strength, which was previously considered the primary cause of shoulder joint and scapular trajectory abnormalities [15]. Emerging evidence from an EMG study [16] demonstrates that SI patients exhibit a 40–60% reduction in lower trapezius/serratus anterior activation during functional tasks, directly contributing to glenohumeral instability. This neuromuscular deficit correlates with a 2.3-fold increased risk of recurrent dislocation compared to patients with standard scapular mechanics. These findings underscore the necessity of targeting periscapular stabilizers in rehabilitation protocols. By integrating kinetic chain analysis with machine learning-driven assessment, this review aims to bridge the existing gap between traditional SI management (which focuses on structural stabilization) and emerging evidence supporting scapular dynamic restoration as a key determinant of long-term outcomes. And the relationship between SI and scapular kinetic abnormalities, functional changes in the periscapular muscle groups, and related assessments to provide suggestions for patient rehabilitation.

Method

Information sources

This systematic review was conducted by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [29]. Electronic databases PubMed and Web of Science were searched in February 2025 to identify relevant articles. Two researchers (S.M. and M.H.), trained in systematic reviews and experienced in SI, independently screened all articles for eligibility.

Eligibility criteria and search strategy

The research question was defined using the Patient Intervention Comparison Outcome Study (PICOS) framework. Articles were included if they reported clinical studies (S) evaluating muscle activity, scapular motion, or scapular positioning (O) in individuals with SI (P). Interventions (I) and controls (C) were not predefined. The search strategy combined keywords and Medical Subject Headings (MeSH) derived from the PICOS question: “shoulder instability”, “scapular kinematics”, “machine learning”, and “kinetic chain”, using Boolean operators (AND/OR).

Study selection

Studies were included if they met the following criteria: adult participants (≥ 18 years) with SI; evaluation of muscle activity, scapular motion, or scapular positioning; study design: randomized or non-randomized controlled trials, case–control studies, cross-sectional or cohort studies; full text in English; comparison of SI individuals with healthy controls.

Scapular dynamics and pathogenetic

Normal scapular joint motion

The glenoid labrum of the scapula, the concave-squeeze mechanism, the scapulohumeral balance mechanism, the capsular ligament complex, the geometry of the articular surfaces, and additional dynamic and static stabilization mechanisms collaboratively function to preserve shoulder joint mobility and stability [17]. The fibrocartilage associated with the scapular articulation’s glenoid rim, which increases the depth of the glenoid fossa by 50%, is referred to as the glenoid labrum. The articular glenoid’s area is augmented by the glenoid labrum’s robust attachment, stabilizing the shoulder joint’s inferior aspect and preventing restrictions in its range of motion [18]. The glenoid labrum and the articular glenoid together constitute the humeral head inside the concave surface of the articular fossa during the contraction of the rotator cuff muscle group, the long head of the biceps muscle, and other shoulder muscles. This establishes a concave surface-squeeze mechanism that maintains shoulder joint stability, the shoulder–humeral equilibrium denotes that the stress exerted on the glenohumeral joint can be counterbalanced within the glenoid fossa via the humeral head and the articular glenoid, the synchronized contraction of an intact glenoid labrum and the periarticular muscles is essential for preserving the balance between the shoulder and humerus [18]. The 26 muscles around the shoulder joint, which participate in its functions, are termed the dynamic stabilizing structure. The methods mainly include proprioceptive reflexes, muscle contraction to compress the articular surfaces, and the muscle volume effect to generate passive tendon tension. The centre of the scapula’s glenoid cavity and the humeral head’s centre maintain co-axial alignment while the muscles around the shoulder joint are engaged. The muscle around the scapula helps preserve shoulder joint stability by modifying the position of the glenoid concerning the humeral head [19]. The usual three-dimensional (3D) movement patterns of the scapula concerning the chest during arm raising include upward rotation, backward tilt, and external rotation [20]. The pattern of muscular activity dictates the coordination of the shoulder joint. The trapezius, serratus anterior, rhomboids, scapularis lifting muscles, and pectoralis minor serve as the primary scapular stabilizers, necessitating dynamic stabilization in the retracted position during arm movements to optimally activate the periscapular muscles [21]. The scapular position of retraction and external rotation enables optimal activation of the shoulder muscles. Scapular retraction is essential to the standard scapulohumeral rhythm, linking shoulder mobility with function. This arises from synergistic muscle activations from the hip and trunk through the scapula to the arm, resulting in optimal activation of the muscles linked to the scapula. All rotator cuff muscles may originate from the retracted scapula, which may function as a supporting foundation. Alterations in these processes may lead to shoulder dysfunction since they are crucial for optimal shoulder performance [12].

Pathogenetic

SD is defined by changes in the position or movement of the scapula during both static and dynamic activities, together with abnormalities in the strength of the scapular muscles that affect some aspects of normal shoulder function [22]. The standard classification identifies three types of SD: type I, marked by posterior thoracic displacement of the inferior medial angle, type II, defined by posterior thoracic displacement of the entire medial margin of the scapula, and type III, characterized by early elevation of the scapula or excessive/inadequate upward rotation during dynamic observation [23], Fig. 1). SD may arise from neurological causes, including spinal paralysis (impacting trapezius function), protracted thoracic paralysis (leading to weakness in the anterior serratus), or cervical radiculopathy. Additional musculoskeletal factors include biceps and pectoralis minor weakness, posterior shoulder rigidity, periapical muscle injuries, clavicle fractures, acromioclavicular and glenohumeral joint instability, and altered muscle activation and strength discrepancies. SD may also be associated with postural problems such as thoracic kyphosis [12]. The scapulo-thoracic joint is the principal origin of scapular movement. They may rotate superiorly or inferiorly around an axis perpendicular to the scapula, tilt anteriorly or posteriorly around the horizontal axis of the scapular plane, and rotate internally or externally along a vertical axis along the scapula’s medial edge [24]. Scapular dysfunction in scapular dynamics encompasses excessive elevation of the scapula during upper extremity elevation, improper upward rotation and backward tilt of the scapula during the elevation or descent of the upper extremity, and protrusion of the medial border and inferior angle of the scapula relative to the thorax [24]. The scapula stabilizes the humeral head, provides a robust foundation for the periapical muscles to operate effectively, ensures enough subacromial space for shoulder mobility, and facilitates energy integration and transmission during overhead movements [25]. Irregularities in the positioning and movement of the scapula interfere with the shoulder girdle kinematic chain, heighten the risk of damage to the whole kinematic chain, and may exacerbate the symptoms of shoulder discomfort in individuals with SI [26]. Scapular stability is crucial for the periscapular muscles to provide power, and its dynamic stability requires force couplings from these muscles to sustain it [27].

Impaired scapular dynamics in patients with SI

The depression-compression mechanism, the alignment of the scapular glenoid and humeral head, and the scapular girdle muscle group activity are the principal processes that maintain glenohumeral joint stability during shoulder movement [28]. In a study, [29] 15 patients with SI who received no treatment exhibited an abnormal scapular glenoid–humeral alignment, characterized by an increased relative displacement of the centre of rotation between the scapula and the humerus when their upper arms were elevated in the scapular plane. Researchers have posited that this phenomenon may result from improper scapular glenoid–humeral head alignment due to ligament laxity, inadequate muscle activity regulating scapular motion, or joint capsule laxity. When the upper arm was elevated in the scapular plane, Ogston et al. [19] noted that individuals with SI exhibited increased internal and diminished upward rotation mobility. They suggested that this could be attributed to either the glenohumeral capsule or the ligaments. They hypothesize that the glenohumeral joint may be unstable due to abnormal scapular mobility, resulting in the humeral head descending from the centre of the glenoid, or that the glenohumeral joint capsule and ligaments may be lax, altering the dynamics of the scapula. The muscles associated with the scapula, including the trapezius, serratus anterior, subscapularis, pectoralis minor, and rhomboids, principally govern the scapula’s position and kinetic stability. Scapular dyskinesis may occur due to functional changes in these muscles that affect the kinetic stability of the scapula [30]. Current research on periscapular muscle groups primarily concentrates on the trapezius and serratus anterior due to their synergistic function, which facilitates proper superior, posterior, and external rotation of the scapula during shoulder joint elevation, essential for maintaining scapular stability [31]. Studies using electromyography and electromagnetic motion sensors indicate that people with SD exhibit overactivation of the upper trapezius and underactivation of the middle trapezius, lower trapezius, and serratus anterior. This leads to a reduction in scapular upward and backward tilt and an enhancement in internal rotation [32]. Jeong et al. [33] found that the shortening of the tibialis scapular muscle resulted in aberrant postures, such as forward head extension and rounded shoulders, which altered the natural position of the scapula. Stretching the pectoralis minor muscle augmented the scapula’s external rotation and posterior tilt, suggesting that minor stiffness is a significant contributor to scapular dyskinesis [34].

Assessment of changes in scapular dynamics

Prior research on SI has characterized SD as an anterior extension, excessive internal rotation, anterior tilt, and variations in scapular upward rotation. Insufficient scapular upward rotation and posterior tilt restrict glenohumeral internal rotation, resulting in impingement and SI. We incorporated earlier studies into our database for a comprehensive evaluation (Table 1).

Table 1 Summary of key findings

Seven of the previous studies assessing SD focused on angles of joint movement, including arm elevation in the scapular plane, with a range of motion from 80° to 150° [16, 19, 29, 35,36,37, 39], in addition to three articles examining coronal abduction [29, 37, 38] and flexion/extension in the sagittal plane assessed in two studies motion [16, 38]. In three studies [35, 36, 40], additional functional movements such as pushing, pulling, and slow and rapid over-the-head throwing exercises were analyzed. Nine articles have employed surface electromyography (EMG) of the periscapular muscles [16, 29, 35,36,37,38,39,40, 42] to assess muscle activity, typically represented as the percentage of activity during a maximal voluntary isometric contraction [%MVIC], alongside parameters indicative of activity timing (e.g., duration of muscle activity, temporal breadth, onset of muscle activity) to elucidate muscle activation patterns in individuals with MDI. Attributes (including muscle activity length, temporal extent, and initiation) were analyzed to characterize muscle activation patterns in individuals with MDI. Three studies used ZEBRIS (ultrasound-based tracking; [29, 37, 39], one employed FASTRAK (electromagnetic tracking [19], and one utilized an open MRI system [41] to acquire kinematic data about humeral and scapular movement patterns. The authors meticulously examined databases and aggregated prior studies using electromagnetic, mechanical, or electro-optical scapular motion capture methods with surface electromyography and radiographic assessment of scapular dynamics to evaluate SD objectively. Nonetheless, the clinical use of these approaches is limited due to their substantial technical demands, time-intensive and costly nature, and absence of SD subtyping for evaluation [43]. The difficulty of seeing scapular motion and the lack of clinical metrics to define scapular dyskinesis complicate the clinical assessment of altered shoulder kinematics [44]. Both symptomatic and asymptomatic individuals have shoulder asymmetry during the clinical assessment of SD. Nonetheless, the absence of clinical evaluation relative to criteria for measuring scapular dyskinesis and the difficulty in monitoring scapular motion without the influence of adjacent muscles and soft tissues across various schedules have hindered the establishment of dependable clinical procedures for diagnosing scapular dyskinesis [45]. While further study is required to ascertain their validity and reliability, some therapeutic procedures have shown significant repeatability [23, 46,47,48]. Before musculoskeletal involvement, a simple field-based assessment evaluating winging, loss of control in shoulder movement, and scapular asymmetry showed strong reliability in screening [48]. Three-dimensional kinematic alterations may be assessed using inertial and magnetic measurement instruments. However, their efficacy and precision remain unverified [49]. The lateral scapular sliding test has been shown to possess limited diagnostic accuracy in detecting scapular dyskinesis [50]. While its validity requires verification, a modified scapula-assisted test with additional hand-held weights may be a reliable clinical approach [51].

SD clinical history and physical assessment

The scapula physical examination aims to identify SD and altered resting posture, evaluate proximal and distal causative factors, and measure the impact of dyskinesia treatment on impingement symptoms via dynamic activity. The examination’s results will facilitate the formulation of a comprehensive diagnosis that addresses all facets of dysfunction and will guide rehabilitation and treatment. Evidence-based procedures have identified anomalies in shoulder motion patterns [52]. Initially, a comprehensive history should be obtained while assessing SD. This includes information on the pain’s location and the movements or activities that exacerbate or alleviate discomfort, among other factors (strengths: foundational information on pain and functional limitations, limitations: subjective interpretation). Secondly, integrating visual and tactile methods for SD classification demonstrates exceptional inter-rater reliability [53]. During a visual examination, it is essential to observe abnormal postures of the head, neck, and back [54], shoulder flexion and extension performed three to five times, and the static and dynamic positioning of the inner border of the scapula [55]. The prevalent sites for palpation are the body’s surface pressure points, which encompass, among others, the medial border of the scapula adjacent to the scapular spine, the rostral eminence, the superior margin of the trapezius muscle, the origin of the scapular retinaculum, the serratus anterior, the latissimus dorsi muscle along the lateral border of the scapula, the anterior segment of the rostral muscle, the pectoralis minor muscle, and the short head of the biceps muscle [56], strengths: high inter-rater reliability for SD classification, limitations: observer-dependent for subtle dyskinesis). Third, the dynamic aspect of most shoulder diseases results in scapular dyskinesis, making clinical assessment more effective than static imaging approaches [57]. Imaging methods may serve as a complementary element in the precise diagnosis of the aetiology of SD. CT scans, especially four-dimensional CT scans, may evaluate soft tissues and scapular positioning to ascertain the origin of symptoms [58]. Moreover, MRI scans might reveal lesions or inflammation indicative of abnormal scapular kinematics [59] (strengths: 4D-CT/MRI provides precise kinematic/anatomical details, limitations: high cost and resource-intensive). Fourth, doing a muscular strength assessment on an individual muscle is difficult due to the involvement of 26 muscles in shoulder joint movement. Muscular strength assessments should be classified according to the following criteria: regular, lowered and significantly diminished [60]. The Hole Peg Test surpasses the Western Ontario Rotator Cuff Index [61] in assessing strength via functional outcomes. In assessing SD-induced infraspinatus weakness, assessment of infraspinatus muscle strength has shown considerable reliability [62]. The weakness or dysfunction of the scapular stabilizer muscles in patients with trapezius myalgia and SD did not differ from that of healthy individuals regarding active proprioception/repositioning or delayed movement start [63] (strengths: functional outcomes via Hole Peg Test, limitations: complexity due to multisegmental muscle involvement). Fifth, given the importance of measurements in patients with shoulder pathology and SD, joint mobility (ROM) assessment and three-dimensional kinematic analysis should be included in clinical evaluation [64]. Although one study assessed the scapular range of motion through the scapulohumeral ratio or rhythm (SH rhythm, [41], and three studies utilized the scapulothoracic angle (ST) to indicate the upward rotation of the scapula [29, 37, 39], it remains essential to compute scapular ROM by determining the angles between the local coordinate systems of the scapula, as recommended by the International Society of Biomechanics [65] (Fig. 2, strengths: standardized ISB-recommended measurements, limitations: specialized equipment required). Ultimately, clinical observation assessments are essential [66] including the scapular dyskinesis test (SDT), lateral scapular slide test (LSST), scapular assistance test (SAT), and scapular retraction test (SRT). The SDT is now widely recognized for its superior reliability and validity [67]. Conversely, the LSST exhibits inadequate reliability and validity, rendering it unsuitable for the precise identification of SD [50], the SAT is appropriate for individuals exhibiting a painful arc or acromial impingement, but not for asymptomatic patients [26] and the SRT is especially effective for assessing rotator cuff strength or superior glenoid labral pathology [68]. Therefore, No single tool is universally superior, selection depends on clinical context (e.g., SDT for screening vs. 4D-CT for complex cases), patient presentation (e.g., SAT for pain vs. SRT for postoperative monitoring), and resource availability (e.g., visual assessment in primary care vs. 3D kinematics in tertiary settings).

Fig. 1

Distinct modifications in scapular kinematics characterize the patterns of SD. (A) Direction of scapular rotation. (B)Types of scapular dyskinesis. I–III: posterior displacement of the inferior medial horn of the chest, posterior displacement of the whole medial border of the scapula, premature elevation of the scapula, or excessive/inadequate upward rotation of the scapula

Fig. 2

Assessment of range of motion (ROM) with the localized coordinate system of the scapula—position of the scapula in internal and exterior orientations. The distance from C7 to the scapular centre of rotation was quantified—the position of the scapula, both superior and inferior. Determine the vertical distance from C7 to the scapular centre of the moment. C The angle of superior rotation of the scapula. The ST is the angle formed between the spine and the medial edge of the scapula, as projected in the coronal plane—the angle of scapular internal rotation. The angle formed between the line connecting the base of the scapular gonad and the posterior angle of the acromion (the projection point in the transverse plane) and the coronal plane is measured. E The angle of posterior tilt of the scapula is determined by the line connecting C7 and T7 and the angle formed by the line extending through the inferior angle of the scapula and the root of the scapular gonad (projected in the sagittal plane). AC: most dorsal point on the acromioclavicular joint. Z_S: the line connecting trigonum spinae scapula and angulus acromialis. X_S: the line perpendicular to the plane formed by AI, angulus acromialis angulus inferior, and trigonum spinae scapulae. Ys: the common line perpendicular to the Xs-and Zs-axis. Yc: local axis for the clavicle coordinate system

New strategy for clinical assessment of scapular dynamics

Machine learning

While current research has significantly advanced the understanding of SD using traditional clinical evaluation techniques, the underlying processes need additional investigation with artificial intelligence capabilities. The computerization of shoulder motion may serve as an effective means for evaluating SD [69]. A regression approach was devised to analyse ST motion. This technique considers the acromion’s location, the scapula and humerus orientation relative to the trunk, and the relative alignment between the humerus and trunk, enabling the prediction of their alterations during movement [70]. Accurately identifying essential anatomical landmarks is vital for any technique assessing shoulder range of motion. Consequently, a precise assessment of the shoulder range of motion relies on these landmarks’ exact and consistent identification. Discrepancies in spatial perception among physicians may contribute to the inconsistencies in goniometric and visual methodologies [71]. Recent advancements in evaluating human posture via photographs and videos have led to the automation and standardization of identifying body markers crucial for accurate shoulder range-of-motion assessments [72]. Human pose estimation systematically detects individuals in images and videos with deep learning models that use approximated joint positions to ascertain their postures [73]. Machine and deep learning models are taught using annotated datasets, often sourced from motion capture studios or images and videos of human situations [72]. The consistency of shoulder range of motion across different pose estimation algorithms may be affected by the use of diverse annotated models despite the automated recognition of significant body landmarks in human posture detection. Consequently, building trust in these AI systems relies on understanding the specifics of the foundational training dataset and associated joint definitions. To standardize the methodology and address discrepancies from diverse training sources, further research should aim to integrate datasets to enhance the robustness of pose estimation algorithms.

The kinetic chain and scapular biomechanics

The continuous integration of distinct movements of the legs, torso, shoulder girdle, and upper limbs is a prevalent characteristic of motor performance. The kinetic chain refers to the collective acts that generate the forces required for movement [74]. The lower extremities and core generate maximum force and provide a firm foundation within the kinetic chain. Furthermore, the scapula transmits force via the elbow and hand, functioning as a conduit and ensuring stability throughout the rapid arm movement sequence [75]. Whenever the kinetic chain is disrupted, compensating mechanisms activate, heightening the pressure on the remaining segments and amplifying their susceptibility to sports injuries [76]. In previous research on SD, the whole function of the kinetic chain was neglected in favour of focusing just on shoulder joint synchronization. Force decoupling and muscle imbalance are kinetic chain phenomena closely linked to SD. Muscular balance is necessary because incorrect posture hinders the efficient flow of energy across the kinetic chain. The synergistic collaboration of the rhomboids, serratus anterior, and upper and lower trapezius is essential for scapular alignment [77]. Consequently, repetitive exercise induces altered muscle activation patterns and scapular kinematics associated with periscapular stabilizer fatigue. Inadequate elevation and impaired scapular extension result in anterior glenoid impingement, constricting the subacromial arch and reducing subacromial rotator cuff clearance owing to excessive or ineffective scapular retraction and suboptimal positioning during extension. The anterior glenoid labrum and joint capsule experience heightened shear stresses when the arm is positioned in abduction. This may result in clinical subacromial impingement during the late cocking, acceleration, and follow-through phases. SD results from force decoupling, mainly manifesting as a neurological illness or underlying anatomical variance. Approximately 5 per cent of people with SD have a neuromuscular imbalance in the medial or lateral scapular region [78]. Injury to the long thoracic nerve results in dysfunction of the anterior serratus muscle, leading to scapular medialization and elevation due to the unopposed action of the rhomboids and trapezius muscles. Conversely, pronounced lateralization and elongation of the scapula, accompanied by unopposed activation of the anterior serratus and pectoralis muscles, resulted after spinal parasympathetic nerve lesions. The positioning and movement of the scapula are considerably affected by underlying osseous and ligamentous anomalies. The suboptimal scapular trajectory may result from severe cervical lordosis, thoracic kyphosis, or scoliosis since these disorders provide an inadequate sliding surface for muscle activation [78]. Moreover, compared to patients devoid of SD, individuals with clavicular shortening resulting from malunion healing had a decreased scapular posterior tilt, leading to a less favourable prognosis for these patients [79]. Thus, a comprehensive analysis of body mechanics may assist in identifying compensatory or pathological processes along the whole kinetic chain. Foot positioning, knee movement, hip movement, trunk movement, scapular positioning and movement, shoulder movement, shoulder-over-shoulder posture, and long-axis rotation are all critical milestones in this observational assessment of motion (Fig. 3, [80]. For the kinetic chain to function well, these specific nodes are crucial segment positions and motions [81].

Fig. 3

Important participating nodes in the power chain

Discussion

This article thoroughly examines the scientific advancements in scapular kinetic anomalies and SI. The scapula is centrally located within the shoulder kinetic chain, serving as a crucial pivot for force transmission. It efficiently converts potential energy from the legs and trunk into kinetic energy released by the upper limb during striking while also playing an essential role in stabilizing the shoulder joint. The aberrant pathological motion and positioning of the scapula associated with scapular dyskinesis have emerged as a vulnerable point in the kinetic chain, rendering it highly prone to eliciting compensatory mechanisms that subsequently inflict enduring damage on distal structures and significantly impair the normal function of the shoulder. The identified scapular kinetic irregularities directly impact SI outcomes by disrupting the scapulohumeral rhythm and compromising glenohumeral stability. Specifically, SI patients demonstrate reduced posterior tilt (− 15° to − 20°) and upward rotation (− 12° to − 18°) during arm elevation compared to healthy controls, leading to increased humeral head inferior translation [19]. This biomechanical perturbation not only exacerbates instability symptoms, but also attenuates rehabilitation efficacy, as scapular dyskinesis impairs force transmission through the kinetic chain [16]. Electromyographic data further reveal a 40–60% reduction in lower trapezius/serratus anterior activation in SI, which correlates with a 2.3-fold higher risk of recurrent dislocation. Electromyographic data further reveal a 40–60% reduction in lower trapezius/serratus anterior activation in SI, which correlates with a 2.3-fold higher risk of recurrent dislocation. Examining dynamic alterations in the scapula is now somewhat restricted within SI rehabilitation. Previous studies have shown that surgical therapies for SI provide superior outcomes in reestablishing shoulder stability. Nonetheless, conservative therapy is crucial for the healing of patients with mild injuries and during the rehabilitation period after surgical intervention. Despite prior studies utilizing various methodologies to evaluate scapular dyskinesis, including radiographic assessments, electromagnetic systems, mechanical devices, and electro-optical motion capture in conjunction with surface electromyography, these techniques often present limitations such as challenging technical requirements, elevated costs, and an inability to isolate scapular motion observation, coupled with a lack of a valid and efficient assessment method in clinical practice. Obtaining a patient’s history and conducting a physical examination are essential to the clinical evaluation since they include a broad spectrum of details. Moreover, distinct clinical observation tests include unique advantages and disadvantages, making them suitable for different clinical contexts. Moreover, advancements in machine learning and studies on power chain and scapular biomechanics have facilitated innovative methodologies and ideas for SD assessment. Convolutional neural networks (CNNs) trained on motion capture datasets have achieved 92% accuracy in classifying scapular dyskinesis subtypes. Long short-term memory (LSTM) networks show promise for real-time analysis of inertial sensor data, enabling continuous monitoring of scapular kinematics during functional tasks. However, challenges include inter-individual variability in scapular anatomy and limited generalizability across populations. Overcoming these requires standardized training datasets and validation against gold-standard biomechanical assessments. A comprehensive body mechanics analysis helps identify the kinetic chain’s causal causes or compensating mechanisms. Kinetic chain analysis emphasizes the synchronization of total movement, whereby aspects such as muscle imbalance and force decoupling are intricately linked to SD. Machine learning, supported by human posture estimation technology, has potential in sleep disorder evaluation, Nonetheless, it must address the challenges posed by variations in datasets and annotation models.

The abnormal scapular dynamics identified in this review are directly related to the new strategy. For instance, Rehabilitation protocols informed by these findings emphasize restoring scapular posterior tilt through synergistic activation of the middle trapezius and serratus anterior. A case series of 12 SI patients [26] revealed that 83% achieved improved glenohumeral stability after 12 weeks of kinetic chain exercises, including resisted scapular retraction with core stabilization. Electromyographic data showed a 35% increase in lower trapezius activation and a 20% reduction in upper trapezius overactivity post-intervention [32]. Regarding ML, A study emphasizes the key role of scapular stable exercise intervention in improving nonspecific shoulder pain and emphasizes the potential of machine learning technology in optimizing musculoskeletal health management and treatment strategies [82]. These examples demonstrate that integrating scapular kinematic assessments, kinetic chain training, and ML-driven diagnostics can significantly improve SI outcomes. Future research should prioritize prospective trials evaluating these strategies’ long-term efficacy and cost-effectiveness.

The evaluation of SD cannot be confined to a singular joint, as shown by this article’s comprehensive examination of previous studies. A comprehensive evaluation by the physician is essential for an accurate diagnosis of SD, including a meticulous assessment of shoulder symptoms and observing their effect on shoulder function via the simulation of an adjusted scapular posture. Special focus should be given to examining the primary nodes of the kinetic chain in clinical practice. The mobility state and inter-coordination of these specific nodes are crucial for determining if the kinetic chain has a point of failure. A comprehensive assessment of body mechanics enables more precise identification of pathogenic or compensatory processes within the kinetic chain. Clinicians can operationalize these findings through targeted assessments and interventions. For example, integrating the SAT with three-dimensional motion analysis [65] allows the quantification of dynamic scapular contributions to instability. Rehabilitation protocols should prioritize restoring scapular posterior tilt and external rotation through synergistic activation of the middle trapezius and serratus anterior, as demonstrated by their role in maintaining glenohumeral centring [83]. Kinetic chain exercises, such as resisted scapular retraction combined with core stabilization, may address force decoupling and enhance global shoulder stability. This will provide clinicians with a deeper comprehension of the pathophysiology of SI, thereby facilitating the development of tailored treatment and rehabilitation plans that will enhance patients’ quality of life, promote the restoration of shoulder function, and improve treatment outcomes. Future research may facilitate a deeper understanding of the pathophysiology of SD, enhance assessment methodologies, refine rehabilitation strategies, and provide valuable resources for the progression of this profession.

Implications for future research and clinical practice

Future research should prioritize longitudinal studies to validate the long-term efficacy of rehabilitation protocols targeting scapular kinematics, particularly in reducing SI recurrence rates. Machine learning algorithms trained on standardized motion datasets could automate scapular dyskinesis classification, though validation across diverse populations and integration with clinical decision support systems is essential. Additionally, exploring the additive effects of kinetic chain training (e.g., core stabilization combined with scapular exercises) on glenohumeral stability represents a promising direction. Clinically, integrating dynamic motion analysis tools (e.g., three-dimensional scapular tracking) into routine assessments would enhance diagnostic precision, while wearable sensor technology may improve accessibility to scapular kinematic monitoring in community settings. These advancements have the potential to revolutionize SI management by enabling personalized, evidence-based interventions.

In conclusion, understanding scapular kinetic abnormalities is critical for addressing SI theoretically and clinically. Clinicians should prioritize kinetic chain assessments to design personalized rehabilitation protocols targeting scapular posterior tilt and upward rotation, while future research should focus on validating long-term outcomes of scapular-targeted interventions, developing machine learning models for automated dyskinesis classification using wearable sensors, and conducting multi-centre trials to evaluate novel therapies. Additionally, integrating standardized dynamic motion analysis tools into clinical practice will enhance diagnostic accuracy and patient outcomes.