The Unstable Shoulder
There is new classification surrounding an unstable shoulder. Based on the Stanmore classification of shoulder instability there are 3 types:
Polar type I (structural instability), Polar type II (Atraumatic instability), and Polar type III (Neurological dysfunction/muscle patterning). This can be simplified to Born loose, Torn loose, Worn Loose.
Polar Type I:
The Unstable shoulder may present with general rotator cuff weakness, and positive apprehension test, while also showing deficits particularly in subscapularis with a lift-off test. As this type begins to progress a patients shoulder may exhibit increased scapular dysfunction, and abnormal muscle activation. Imaging should only be used when there is suspected structural instability, with arthroscopy being useful to pinpoint areas causing instability.
Polar Type II:
May present with increased capsular laxity, excessive ER, a sulcus sign, and potentially GIRD. Abnormal anterior translation may be present due to laxity, scapular dyskinesia, muscle imbalance, and congenital labral pathology.
Polar Type III:
Will present with large muscle activation occurring (Lat Dorsi, Pec Mj, Ant Delt, and Infraspinatus) while other rotator cuff muscles may be suppressed.
What can you do for an unstable shoulder?
Imaging can be used on the unstable shoulder using X-ray at first to gain an insight into the structural damage done and the position of joint. CT and MRI can be used when diagnoses is still unclear and soft tissue imaging could be of greater benefit.
Each polar type causes different mechanisms for instability and pain. It can be helpful to classify patients to better manage symptoms and create the appropriate exercise program. Physiotherapy can be beneficial to help manage symptoms and limit risk of dislocations.
Each program should be tailored to each patient, however early stages should start with regaining ROM, with AAROM or PROM to help normalise the movement. While Isometrics can be used to help with muscle activation, and proprioception (hands on table) to help with joint stability.
Once joint stability has been restored the patient can progress. Progression is to include increased strengthening within varying ranges, and stabilisation exercises (wall ball, wall push ups).
The Unstable shoulder final stage of rehab can include a progressed exercise program. This includes plyometric work and increased dynamic movements and stability work, along with return to sport/work activities.