Primary
Due to ST articulation disorder
1. Neurological
A. Spinal accessory nerve / Trapezius palsy
- iatrogenic (lymph node biopsy)
- stab wound
B. Long thoracic nerve / Serratus anterior palsy
- iatrogenic (mastectomy)
- trauma
- repetitive microtrauma / swimming
C. Dorsal scapular nerve / Rhomboids palsy (rare)
2. Osseous
Osteochondromas
Fracture Malunions
3. Soft Tissue
Muscular origin
- traumatic ruptures of Serratus Anterior
- iatrogenic / thoracotomy
Secondary
Due to GHJ articulation disorders
A. Erb’s palsy
- compensatory for IR contracture
B. Deltoid fibrosis
- injury or repeated IM injections
C. Painful conditions
- i.e. RC tear, fracture, impingement
- compensatory
Voluntary
Rare