This prospective case series defines functional shoulder instability (FSI), a form of instability caused by pathologic muscle activation rather than structural defects. Using clinical scores, dynamic fluoroscopy, MRI, and psychological screening, the authors characterize FSI subtypes. They propose a 4-part classification based on pathomechanism and volitional control.
When a young patient demonstrates their own shoulder subluxation with no structural lesion on MRI, think functional shoulder instability driven by abnormal muscle activation, not a Bankart problem.
The practical decision rule is built on two axes: is the instability positional (triggered by arm movement) or nonpositional (occurring in neutral position from muscle contraction), and can the patient control it?
That controllability axis matters most. Controllable FSI causes little impairment and should be left alone. Noncontrollable FSI is disabling but still should not be operated on, because surgical outcomes are unpredictable and sometimes catastrophic.
This paper's most useful teaching point is restraint. These patients often look bizarre, have failed multiple treatments, and get mislabeled as psychiatric, yet formal screening found no severe disorder. Get an MRI, avoid overinterpreting minor lesions, and direct them toward targeted rehab with coordination and biofeedback rather than a stabilization procedure.
This prospective case series defines functional shoulder instability (FSI), a form of instability caused by pathologic muscle activation rather than structural defects. Using clinical scores, dynamic fluoroscopy, MRI, and psychological screening, the authors characterize FSI subtypes. They propose a 4-part classification based on pathomechanism and volitional control.
When a young patient demonstrates their own shoulder subluxation with no structural lesion on MRI, think functional shoulder instability driven by abnormal muscle activation, not a Bankart problem.
The practical decision rule is built on two axes: is the instability positional (triggered by arm movement) or nonpositional (occurring in neutral position from muscle contraction), and can the patient control it?
That controllability axis matters most. Controllable FSI causes little impairment and should be left alone. Noncontrollable FSI is disabling but still should not be operated on, because surgical outcomes are unpredictable and sometimes catastrophic.
This paper's most useful teaching point is restraint. These patients often look bizarre, have failed multiple treatments, and get mislabeled as psychiatric, yet formal screening found no severe disorder. Get an MRI, avoid overinterpreting minor lesions, and direct them toward targeted rehab with coordination and biofeedback rather than a stabilization procedure.