Hi I understood your concern. Since you have a severe sinus infection, Levaquin is a very good antibiotic and shows good result. Every drug has side effects. Levaquin too has numerous side effects. Levaquin belong to a class of fluoroquinolones. It has been shown to have a safe and effective profile in treating bacterial infections like sinus infection. No need to worry reading about its side effects. Consult your Doctor if you are having any allergic reactions in your body,breathing difficulties,joint pain or any other complications after taking it. If you have kidney or liver diseases, respiratory diseases,muscle weakness,seizures, joint problems etc you should tell it to your Doctor before taking the medication. There is less chance of getting tendon damage or pain like you mentioned. No need to be scared. If you have any serious side effects like I mentioned above, stop the medication and consult the Doctor immediately so he can check the condition and prescribe alternative. Hope this help If you have any further questions you can reply here on health care magic Thank you