23.36 Demonstration

  • “Patient” should stand and hold both arms in abduction at 90

  • One in internal and on in external rotation

  • Internal rotation becomes tired more quickly

Muscle imbalance

  • Any muscle imbalance (particularly in the rotator cuff muscles) alters the direction of the resultant (more upward and medial)

  • This increases the shear force

  • The force vector can migrate beyond the contact area of the gleno-humeral joint… this leads to upward migration of the humeral head

Unlabelled Image MissingKempf 1999[@Kempf1999]