Suggest Treatment For Severe Pain In Arm

My mother is 73 years old having mild BP and sugar. she is suffering from a severe pain in her left arm from her shoulder to her elbow. The pain is more acute when she moves her hand suddenly or when she gets up or strains her left arm. We had an X ray taken but there was no sign of any bone crak or fracture. We consulted an orthopaedic doctor who said this could be on account of sugar and advised some medices and fermentation. but there has been no relief