Brief Answer: due to auto antibodies and immune complexes Detailed Answer: HI, thanks for using healthcare magic Sjorgren's can be primary or secondary. In secondary sjorgren syndrome there are other autoimmune conditions that may be associated with the condition. Primary sjogrens can be associated with muscle, joint and ligament pains as you have described. This is thought to be related to different factors such as multiple autoantibodies (these are chemicals that attack the body's own tissue), immune complexes or infiltration of muscles and joint tissue by lymphocytes. Lymphocytes are part of the immune system. They are different types. It is thought that the auto antibodies or immune complexes may injure the small vessels associated with the muscles. Injury or inflammation to these small vessels ( vasculitis) can cause the muscle and joint symptoms because it affects the blood supply to this areas. I hope this is clear, Please feel free to ask any other questions

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