Module 1: Glenohumeral Joint Instability – Patho-anatomy, Diagnosis and Clinical Management Pathways
1. Definition
- Glenohumeral joint (GHJ) instability is the inability to maintain the humeral head (HH) centered in the glenoid fossa(Abboud & Soslowsky, 2002). It is associated with a pathological increase in the translational movement of the HH that interferes with joint function and / or produces pain.
- GHJ instability represents a spectrum of disorders with overlapping syndromes that range from complete dislocation of the joint to excessive uncontrolled translation of the humeral head, leading to secondary shoulder symptoms.
- Traditionally, the term GHJ instability implied dislocation (HH translation completely over the edge of the glenoid) or subluxation (partial translation of the HH from the centre of the glenoid socket) of the humeral head.
- In recent years it has been recognised that symptoms of instability (apprehension +/- pain) can result from excessive or uncontrolled translations of the HH without frank dislocation or subluxation. These symptomatic translations can be acquired through the stress of repeated microtrauma (such as throwing sports or repetitive gym) or due to congenital alterations in anatomy or collagen type.
- Instability differs from the term ‘laxity’, ‘hyperlaxity’ or ‘hypermobility’. Laxity refers to an asymptomatic hypermobile joint with the ability to maintain centring of the humeral head in the glenoid fossa. The term instability is used when this function is lost and results in symptoms of pain, discomfort, paraesthesia, apprehension, and/or fatigue. (ref)