Adhesive Capsulitis (Frozen Shoulder): Capsular Contracture Mechanism and Biomechanical Spatial Spinal Decompression Chuna Therapy (SART Protocol)

Why Adhesive Capsulitis Must Be Distinguished from Rotator Cuff Disorders

When the shoulder becomes stiff, preventing the arm from being extended behind the back or raised to the side, many individuals mistake this for simple muscle soreness or rotator cuff damage. However, adhesive capsulitis, commonly referred to as frozen shoulder, is a distinct disease entity with a pathomechanism clearly differentiated from rotator cuff tear or subacromial impingement syndrome. Whereas a rotator cuff tear represents a structural discontinuity of tendon tissue, adhesive capsulitis is a contracture-type lesion in which the joint capsule itself, which envelops the humeral head, becomes fibrotic, thickened, and shrunken following an inflammatory response.

A normal joint capsule stretches flexibly, providing ample space for the humeral head to rotate freely within the glenoid fossa of the scapula. However, as adhesive capsulitis progresses, the volume of this joint capsule is physically reduced, causing an absolute loss of the space in which the joint can move, much like being forced into an undersized garment. Due to this pathological specificity, simple muscle relaxation or stretching alone provides limited fundamental benefit, necessitating a precise treatment strategy that targets the fibrotic structure of the capsule itself.

The Three-Stage Pathomechanism of Frozen Shoulder: From Synovitis to Collagen Cross-Linking

Adhesive capsulitis clinically progresses through three stages: freezing, frozen, and thawing, with each stage exhibiting distinctly different patterns of histological change. In the initial freezing stage, synovitis develops within the joint capsule, causing inflammatory pain that persists even at night, with sharp pain occurring in all directions of shoulder movement. During this period, since inflammatory response rather than structural tissue deformation remains the primary pathology, it is important to manage pain while regulating the inflammation to prevent progression into excessive fibrosis.

As inflammation persists, the condition advances to the second frozen stage, during which collagen fibers within the capsular tissue begin to undergo abnormal cross-linking. Notably, thickening becomes prominent in the coracohumeral ligament and rotator interval located anteriorly at the shoulder, structures that constitute the core ligamentous tissue responsible for external rotation of the humerus. When the coracohumeral ligament and rotator interval thicken and shorten due to fibrosis, external rotation of the arm becomes physically blocked, establishing this as one of the most characteristic clinical findings of adhesive capsulitis. Considering this pathophysiology, graded joint mobilization based on the Biomechanical Spatial Spinal Decompression Chuna Therapy (SART Protocol) is designed on the principle of mechanically lengthening the contracted capsule and rotator interval while minimizing reactive synovitis^[1].

Disruption of Scapulohumeral Rhythm: Compensatory Scapular Elevation and Increased Thoracic Rotation

Normal shoulder joint motion is achieved through scapulohumeral rhythm, in which glenohumeral joint movement (rotation of the humeral head within the glenoid fossa) and scapulothoracic joint movement (the scapula gliding along the thoracic cage) coordinate at a consistent ratio. However, when the capsule becomes fibrotic and external rotation is restricted, the body generates compensatory movements to offset this limitation, including excessive scapular elevation and increased thoracic rotation.

This disruption of scapulohumeral rhythm extends beyond a mere problem of the shoulder joint itself, potentially leading to chronic tension in the neck and upper back musculature, myofascial pain syndrome around the scapula, and even worsening of postural thoracic kyphosis. It is clinically common to observe that once the scapular elevation pattern becomes habitual, the upper trapezius and levator scapulae are continuously overused, resulting in secondary muscular pain that becomes intertwined with the original capsular pain of frozen shoulder. Therefore, treatment of adhesive capsulitis requires an integrated approach that considers not only resolving the capsular contracture itself but also normalizing the already-established compensatory pattern of scapulohumeral rhythm.

Differential Diagnosis: Active-Passive Range of Motion, Impingement Signs, and Capsular Pattern Assessment

Accurately distinguishing adhesive capsulitis from rotator cuff pathology is a critical diagnostic procedure in determining treatment direction. The most important differentiating point is the relationship between active and passive range of motion. In the case of rotator cuff tear, the active range of motion when the patient raises the arm independently is limited by pain and weakness, but when the examiner passively moves the patient's arm, it can move relatively close to normal range. In contrast, in adhesive capsulitis, because the joint capsule itself is physically contracted, the passive range of motion is characteristically restricted to the same severe degree as the active range of motion, regardless of how gently the examiner attempts to move the arm.

Furthermore, the Neer sign and Hawkins-Kennedy test, which are characteristically positive in subacromial impingement syndrome, frequently return negative in adhesive capsulitis. This suggests that the source of pain lies not in tendon friction within the subacromial space but in the contracture of the capsule itself. In addition, confirming whether the characteristic sequence of the capsular pattern appears, in which external rotation restriction is most severe, followed by abduction and then internal rotation, serves as an important differentiating criterion. These clear differential diagnostic standards provide the basis for establishing a treatment strategy specifically applied to capsular lesions, as distinguished from rotator cuff pathology.

Application of Graded Joint Mobilization Under the SART Protocol

The Biomechanical Spatial Spinal Decompression Chuna Therapy (SART Protocol) applies graded joint mobilization techniques to fibrotic and contracted joint capsule and rotator interval tissue, gradually lengthening the tissue within a range that does not provoke reactive synovitis. Specific techniques employed in a stepwise manner include long-axis distraction, which reduces compression between joint surfaces and distributes tensile force evenly throughout the capsule; posterior capsule stretch mobilization, which targets the thickened tissue of the posterior capsule for stretching; and controlled end-range oscillation, which applies regulated vibration at the terminal point of the joint's range of motion.

This graded approach aims not to apply forceful pressure all at once, but rather to safely lengthen fibrous contracted tissue stiffened by collagen cross-linking through a progressive increase in load within the range the tissue can tolerate. Since abrupt stretching carries the risk of inducing microscopic damage within the capsule and re-aggravating synovitis, real-time assessment of the patient's pain response and degree of tissue resistance while adjusting intensity constitutes the core principle of this protocol. The trend of progressive lengthening of contracted capsular tissue and restoration of range of motion observed in Bodyall Korean Medicine Clinic's accumulated Chuna manual therapy clinical experience aligns academically with the mechanical lengthening principle of contracted tissue through long-axis distraction and posterior capsule stretch techniques demonstrated in the cited academic study^[2].

Post-Treatment Mechanism: Restoration of Capsular Volume and Normalization of Glenohumeral-to-Scapulothoracic Motion Ratio

Three biomechanical changes are broadly anticipated following sustained management through graded joint mobilization. First, the volume of the capsule, previously reduced through fibrosis, is progressively restored, securing the absolute space in which the humeral head can move within the glenoid fossa. Second, as capsular volume is restored, intra-articular pressure normalizes, resolving the abnormal compressive state within the joint. Third, the motion ratio between the glenohumeral and scapulothoracic joints—namely, the glenohumeral-to-scapulothoracic motion ratio—recovers to within normal range, reducing excessive compensatory scapular elevation and thoracic rotation.

These three mechanistic goals hold considerable clinical significance in that functional recovery of the shoulder joint extends beyond mere pain relief to restoring the natural movement pattern of the entire upper extremity. Although a substantial proportion of adhesive capsulitis cases have been reported to spontaneously resolve over time in the natural course of the disease, given the prolonged functional limitation and secondary musculoskeletal compensation that occur during this process, a manual therapy approach that directly targets the contracted tissue of the capsule itself is regarded as a biomechanical conservative treatment alternative that can be safely considered prior to surgical intervention.

Comparison of Stage-Specific Characteristics and Approaches for Adhesive Capsulitis

Conclusion: The Need for Precise Approaches to Capsule-Specific Pathology

Adhesive capsulitis is a fibrotic contracture disease of the capsule itself, clearly distinguished from rotator cuff tear or subacromial impingement syndrome, progressing through a clear pathological sequence from synovitis to collagen cross-linking. Restriction of external rotation due to thickening of the coracohumeral ligament and rotator interval, and the resulting disruption of scapulohumeral rhythm, constitute the core biomechanical characteristics of this condition. Following precise differential diagnosis through comparison of active versus passive range of motion, impingement sign testing, and capsular pattern assessment, an approach utilizing graded joint mobilization such as the Biomechanical Spatial Spinal Decompression Chuna Therapy (SART Protocol) to safely lengthen contracted tissue promotes normalization of shoulder joint function.