Hi & Welcome. The most common side effects of statins like Rosuvastatin include stomach upset, liver dysfunction and myopathy. Myopathy (muscle pain, weakness, tenderness) is the serious effect that affects up to 10% of patients receiving statin therapy. Some studies suggest that typical onset of muscle symptoms can range from one week to four years, with a mean duration before onset of 6 months. Based on the history given, you seem to have developed myositis apparently caused by taking Rosuvastatin. I advise you to stop taking Rosuvastatin and consult your treating doctor for further evaluation and to carry out certain lab tests such as creatine kinase to know the extent of muscle damage. Your doctor would prescribe an alternate effective but a safer cholesterol lowering medication like Cholestyramine or Nicotinic acid. Hope this will help.