The Puzzling Pathophysiology of Frozen Shoulder

The Puzzling Pathophysiology of Frozen Shoulder -

Kraal T et al. The puzzling pathophysiology of frozen shoulder- a scoping review. Journal of Experimental Orthopaedics: 2020

  • FS has been described as a self-limiting condition with recovery w/in 2-3 years for most pts. However, sx of mild-moderate pain and stiffness are still reported in 27-50% of pts long-term.
  • The etiology of FS is still poorly understood. Therefore the purpose of this paper is to shed light on the histological findings of inflammation and tissue fibrosis for potential clinical implications
  • This review included 48 articles not published before 1994 due to tissue analysis techniques that may no longer be relevant or appropriate prior to then. Most studies were case control with a small number of pts compared with pts undergoing shoulder arthroscopy for different pathology like instability or RC surgery
  • Some findings: normal shoulder joint as an avg volume of 20 ml, in pts with FS, the volume can be < 5 ml
  • Early stage FS has higher concentration of inflammatory changes identified by hypervascularity and neurogenesis along with fibroplasia. In later stages inflammation resolves but a higher number of fibroblasts and densely packed type III collagen persists.
  • Several authors have hypothesized an association with FS and a chronic state of low grade inflammation. Elevated levels of cholesterol, triglycerides, and blood glucose are often seen in pts with FS compared with controls.
  • DM, CVD, and thyroid disorders are all associated with chronic inflammation and increased levels of pro-inflammatory cytokines are found in pts with FS.
  • More recent studies have found an immune response with an overexpression of inflammatory cytokines is one of the first steps in the development of FS, preceded by a cascade of tissue fibrosis.
  • Other studies have shown that the higher levels of A1c, the higher the incidence of FS. This, along with the inflammatory cascade from DM helps explain the higher incidence among diabetics and the more prolonged conservative treatment is. The accumulation of AGEs may be an important factor influencing A1c levels
  • Chronic states of depression are also linked to FS, possibly b/c of increased inflammatory cytokine levels
  • Clinical implications: the earlier in the disease process a corticosteroid injection is given, the greater the effect on symptoms.
  • Physical therapy mobilization beyond the pain threshold has a NEGATIVE effect due to mechanosensitvity of fibroblasts and increasing the inflammatory response. Mobilization and stretching to tolerable pain levels has been shown to be superior to help collagen remodeling when compared to supervised neglect or wait and see approaches.