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Degree of Instability

The degree of instability (dislocation, subluxation, and microinstability) is also important in determining appropriate treatment options. Dislocation refers to complete dissociation of the articular surfaces of the humeral head and the glenoid cavity.

Subluxation describes increased humeral head translation within the glenoid cavity, where the humeral head translates to the edge of the glenoid without true dislocation. Microinstability in the shoulder joint is a more subtle instability pattern.

Recurrent subluxation may manifest as pain rather than instability. Repetitive, high-energy, overhead activities can cause progressive attenuation of the capsular, ligamentous, and labral structures.

As these static stabilizers fail and the dynamic stabilizers weaken, anterior subluxation occurs leading to impingement symptoms. This results from recurrent microtrauma which can ultimately lead to rotator cuff tearing and destabilization of bicep-labral complex.

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