NEW YORK, NY — You’ve heard of the cold shoulder, but this new study is taking a closer look at a similarly named but all too different phenomenon—the frozen shoulder. New research suggests some people are more susceptible to a frozen shoulder because of their genes. The study reports a sixfold increased risk of having a frozen shoulder if you possess a certain type of risk gene.
Frozen shoulder, formerly known as adhesive capsulitis, is a type of shoulder pain and immobility that happens to 10% of people at some point in their life. People with the condition develop pain and progressively lose shoulder motion. The exact cause of the frozen shoulder is unknown. However, scientists say it may be a number of factors including a prior injury, aftereffect of surgery, to a separate condition that affects shoulder mobility. The loss of shoulder motion comes from the scarring or thickening of the capsule (fibrosis) around the shoulder joint.
There are other factors that have given some insight into what exactly causes frozen shoulder to happen. People with a history of diabetes, thyroid disease, and smoking have all been associated with an increased chance of experiencing a frozen shoulder. More recently, some researchers have observed a higher risk in people with family members who have had a frozen shoulder before—suggesting the condition may be genetic.
To determine if frozen shoulder is a genetic condition, researchers from New York conducted a genome-wide association study to search for specific genes that may be related to frozen shoulder. The team collected genetic data using a large British public database of over 500,000 patients. From 500,000 the sample size was narrowed down to 2,142 patients with a history of adhesive capsulitis along with people without the condition.
Three genes caught the attention of the team. The first was gene variants found in a chromosome site called WNT7B. The finding aligns with prior studies that found a possible link between WNT7B and frozen shoulder along with other orthopedic-related conditions. The other two associations took place on an unreported genetic locus found near genes for POU1F1 and MAU2.
Possessing all three gene variants was linked to a nearly sixfold increase in the chances of having frozen shoulder. Understanding the genetic causes of the frozen shoulder could help researchers know what activates the genes, how to prevent it, and how to best treat it. For example, genes found on the WNT7B loci site are involved in creating bone-forming cells called osteoblasts and regulating fibrosis.
The other two new genetic sites identified in the study play a role in cell division, which could provide a cellular mechanism for how a frozen shoulder occurs in the first place.
The study is published in The Journal of Bone & Joint Surgery.