The scapulothoracic joint is a physiological joint, not a true synovial articulation, formed by the sliding of the anterior surface of the scapula against the posterior thoracic cage. The interface between the subscapularis muscle anteriorly and the serratus anterior posteriorly creates two gliding planes that allow the scapula to rotate, tilt, and protract-retract freely over the ribs. Normal scapular upward rotation of 60 degrees accompanies 120 degrees of glenohumeral elevation to produce full overhead arm reach.
Scapulothoracic dyskinesis, abnormal scapular kinematics, is associated with rotator cuff pathology, shoulder impingement, acromioclavicular joint injury, and thoracic hyperkyphosis. Assessment includes the lateral scapular slide test and dynamic observation of scapular motion during arm elevation. Snapping scapula syndrome involves painful or audible crepitus at the scapulothoracic interface from bursae, muscle tightness, or bony prominences. Rehabilitation targeting serratus anterior and lower trapezius strengthening is the cornerstone of scapular dyskinesis treatment.
Crepitus, popping, or pain at the scapulothoracic interface from bursal inflammation, muscle imbalance, or a prominent superomedial scapular angle produces a characteristic scapular snapping with arm elevation, managed with physiotherapy and occasional surgical bursectomy or scapular angle resection.
Abnormal scapular motion pattern during arm elevation, often with premature elevation or asymmetric rotation, produces shoulder impingement and rotator cuff overload managed with specific scapular stabiliser rehabilitation targeting serratus anterior and lower trapezius.
