SCAPULAR DYSKINESIS

Definition. Scapular dyskinesis is an alteration of the normal position and motion of the scapula during scapulohumeral movements.

What the scapula does. It serves the shoulder in three ways:

• A stable base for the origin of the rotator cuff
• Glenohumeral alignment: the glenoid tracks the humeral head, maintaining ball-and-socket congruency
• Force transfer: an integral link in the kinetic chain, carrying energy from the trunk to the arm

Cause or compensation. Dyskinesis is often a secondary phenomenon, reacting to glenohumeral pathology such as instability, a cuff tear or a SLAP lesion. It then serves as a compensatory mechanism, much as a limp does. Treating the dyskinesis is essential, but the primary pathology must be addressed as well.

Loss of the normal rhythm of scapular motion, seen as dysrhythmia or shuddering, defines dyskinesis, and the topic turns on abnormal scapular movement during elevation. The normal rhythm it departs from is therefore worth stating.

The rhythm varies. Arm elevation combines glenohumeral, scapulothoracic, clavicular and trunk motion, and the contribution of each changes continuously with plane, load, speed, anatomy, fatigue and measurement method. The classic 2:1 ratio is a historical simplification of the whole arc, not a normal threshold.

Coupled scapular motion. Upward rotation, posterior tilt and external rotation usually accompany elevation, coordinated by the trapezius, serratus anterior and other muscles. Pain, glenohumeral pathology, clavicular, rib or scapular structure, neurologic disease and motor adaptation can alter this pattern without establishing a single weak or tight muscle.

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Force couples. Scapular stability relies on balanced force couples, and in dyskinesis these are disrupted. The upper, middle and lower trapezius and serratus anterior coordinate upward rotation, tilt, rotation and thoracic contact; their roles overlap and change with the task.

Soft-tissue restriction. Shortening or stiffness of pectoralis minor or of the posterior shoulder may influence scapular position, but a visual pattern does not prove which tissue is causal.

Neuromuscular adaptation. Pain, fatigue, instability and cuff or clavicle pathology can modify activation and motion as compensation rather than primary disease.

The SICK scapula. Burkhart described this in overhead athletes. SICK is historical language: it describes a proposed throwing-athlete phenotype, not a validated syndrome with reliable diagnostic criteria. Its four elements:

• Scapular malposition at rest, typically depressed and downwardly rotated
• Inferior medial border prominence (winging), due to anterior tilting
• Coracoid pain and tenderness at the pectoralis minor attachment, from traction on the tight pectoralis minor insertion
• DysKinesis, an abnormal movement pattern

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Kibler's patterns. Kibler's classification is a qualitative visual assessment made during elevation. Type I (inferior-angle prominence), Type II (medial-border prominence), Type III (early superior translation) and Type IV (symmetric) are descriptive teaching labels. Their reliability is insufficient for treatment routing, and each pattern can arise from several structures or compensations, so a pattern should not be mapped directly to one muscle.

What to describe instead. For each clinical task, record what you see rather than force a subtype:

At rest. Inspect from behind for asymmetry in resting height and in distance from the spine. Look for pectoralis minor tightness, which shows as a forward shoulder posture, and palpate the coracoid for tenderness.

Push and wall tasks. Use these selectively, to accentuate a suspected neurologic or strength deficit, and interpret them with the nerve and muscle examination.

The winging differential. Long thoracic, spinal accessory and dorsal scapular neuropathy, osteochondroma, rib or clavicle pathology and glenohumeral disorders can create winging or asymmetry, and laterality alone does not distinguish them. Long thoracic palsy is a structural nerve injury that produces medial winging. A snapping scapula, from bursitis or an osteochondroma, presents with crepitus.

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Performing it. View from behind, with clothing adjusted only as necessary and consistent with the patient's dignity. Use unloaded or lightly loaded bilateral elevation and lowering, with several repetitions, enough to reveal the patient's task-specific abnormality, in a plane, at a speed and under a load appropriate to their symptoms and sport or work. Watch the entire concentric and eccentric cycle and the response to fatigue.

Reporting it. Record the side, task and phase; any border or angle prominence, early elevation or shuddering; the fatigue response; and whether the finding is obvious. The preferred report is obvious dyskinesis present or absent. Historical subtypes are optional descriptive language, not reliable categories.

Symptom and performance modification. A positive result on either manoeuvre shows only that manual modification changed the selected symptom or performance measure. It suggests modifiability, not a confirmed diagnosis.

• Scapular assistance test (SAT): assist upward rotation and posterior tilt during the painful task, and record the change in pain or arc
• Scapular retraction test (SRT): stabilise or retract the scapula during the chosen strength or pain task, and record the change without inferring a single weak muscle

Scapular dyskinesis is identified clinically. Imaging is used to rule out other causes, not to verify dyskinesis.

Radiographs. A shoulder series of AP, axillary and outlet views checks for structural causes: an osteochondroma (snapping scapula), fracture malunion or AC joint pathology.

MRI. It looks for the primary cause, such as a rotator cuff tear or a labral (SLAP) tear, and assesses the periscapular muscles for denervation atrophy, seen as oedema or fatty infiltration.

CT. Indicated for a snapping scapula, to visualise rib-cage incongruity or Luschka's tubercle.

Electromyography. EMG is the gold standard if nerve palsy (long thoracic or spinal accessory) is suspected, and differentiates neuropathic weakness from functional inhibition. Performed at an appropriate time, it supports the nerve diagnosis, but it is not infallible.

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Management starts by identifying what the motion finding represents. Functional dyskinesis is treated within rehabilitation of the whole shoulder and kinetic chain; surgery treats a diagnosed structural lesion, not a visual motion label.

Impairment-led rehabilitation. Treat the primary shoulder or neck diagnosis and the pain irritability, then the deficits the examination has found:

• Mobility work only for measured pectoral, posterior shoulder or thoracic restrictions
• Scapular control trained in positions where the patient can succeed, then increased in load, range, speed and kinetic-chain demand
• Serratus, trapezius, cuff, trunk and hip strengthening according to tested deficits, not the historical Kibler subtype
• Return to work or sport when task capacity, symptoms and confidence are restored

The kinetic chain is individual. Screen trunk, hip and task mechanics when relevant, but do not assume a fixed percentage of throwing force or prescribe the same sequence to every patient.

Structural or neurologic cause. Long thoracic or spinal accessory palsy, osteochondroma, rib or clavicle deformity, scapulothoracic bursitis and glenohumeral disease follow their own diagnostic and treatment pathways. Observation, nerve studies, decompression, tumour excision, bursectomy, transfer or fusion are treatments for those diagnoses, not for functional dyskinesis.

There is no operation for scapular dyskinesis itself. Technique, position, fixation and aftercare belong to the named structural procedure and cannot be prescribed from a dyskinesis classification.

• Osteochondroma or other bony prominence: image the ventral scapula and ribs, plan a tumour-safe excision and address the associated bursa when indicated
• Snapping scapula or bursitis: management runs from injection to bursectomy; bursectomy or superomedial-angle resection is reserved for a confirmed structural pain generator after targeted non-operative care
• Nerve palsy: the choice of decompression, nerve or tendon transfer or scapulothoracic fusion depends on the nerve, chronicity, recoverability and disability
• Pectoralis minor release: evidence is limited; reserve it for a clearly diagnosed, refractory structural or tissue problem rather than visual anterior tilt alone

Common harms arise from misclassification: treating compensation as a cause, missing neuropathy or bony pseudo-winging, over-cueing rigid retraction, provoking pain with excessive loading, or performing surgery for a visual sign.

Closed or open chain. Supported and closed-chain options are useful when compression, external support or a reduced lever arm improves control or confidence; they are not inherently safer, nor always the first phase. Open-chain and task options are used when the patient can control the scapula through the required range, load and speed. Progression is criterion-based, and the two can coexist.

Control and endurance. Conscious control can be trained with biofeedback or mirrors, and endurance with low load and high repetition.

Matching exercise to deficit. The observed deficit chooses the exercise category and sets the criterion for progression:

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Postoperative care applies only when a structural diagnosis has been operated on. Wound care, protection, motion and loading follow the actual tumour excision, bursectomy, nerve or tendon transfer or fusion construct. Do not use a generic pectoralis-minor-release calendar for every scapular procedure.

Scapular dyskinesis is a modifiable impairment in some patients and an adaptive or incidental finding in others. Outcome should be the patient's pain, function, strength and endurance, and sport or work capacity, not normalisation of a visual subtype.

Rehabilitation evidence is heterogeneous and usually embedded within broader shoulder programmes, and no defensible universal 80–90% success rate or 3–6 month duration exists. Structural winging outcomes follow the underlying nerve, tumour, bursa or fusion diagnosis.

The Scapular Summit position remains the most transferable: dyskinesis is a potential impairment rather than a discrete diagnosis, and its causal role is not clearly defined. No registry or society algorithm establishes subtype-specific surgery or exercise.

Instrumented 3D or dynamic-radiographic analysis is primarily a research/specialist tool. Access does not replace clinical localization, and asymptomatic athletes frequently show scapular asymmetry.

Related pages: Rotator Cuff Tears, Subacromial Impingement, Anterior Shoulder Instability, and Scapular Winging.