The pathogenesis of frozen shoulder remains unclear. Fibroblast proliferation has been implicated in the pathogenesis with subsequent fibrosis of the capsule. We studied patients undergoing manipulation under anaesthesia for frozen shoulder. All fitted Codman’s criteria for the diagnosis. Normal saline was injected and then aspirated from 15 patients undergoing manipulation under anaesthesia for treatment of frozen shoulder and from 15 patients undergoing shoulder arthroscopy for other pathology. Human fibroblasts were cultured from sections of human anterior abdominal wall obtained from patients undergoing elective surgery. The effect of frozen shoulder aspirate versus normal control on human fibroblast proliferation and apoptosis was measured. Cellular proliferation was determined using the Promega celltitre 96TM non-radioactive cell proliferation assay.

Proliferation of human fibroblasts was significantly increased in the cells treated with aspirate obtained from frozen shoulder patients versus both negative control (growth medium only) and control (normal shoulder aspirate) at concentrations of 105, 25% and 50%. This increase in proliferation was in a dose dependent manner, with the most significant increase seen in cells treated with a 505 concentration of frozen shoulder aspirate. Apoptosis was upregulated at all concentrations of shoulder aspirate, but only achieves statistical significance at 255 and 505 concentrations.

This study supports the hypothesis that frozen shoulder results from alteration in fibroblast regulation.