High school baseball team symptoms and conditions

My son (14 years old) was given levaquin for a sinus and ear infection
2 weeks ago. Around the same time he began practices for his high school baseball team. He complained about his legs being stiff and aching. We assumed it was the intense practices causing his muscles to ache. After a week on the drug, he could barely walk and his knees were swollen. We were very concerned and looked up the side effects of levaquin on the internet. We were shocked and angry when we found out that levaquin should not be given to children under the age of 18 because on the possibility of joint and tendon problems. Today we went to the orthopedist and he drained a lot of fluid off of both knees (it looked like about a 1/2 cup from each).The doctor thinks it has to be a side effect of the drug, because the symptoms began at the same time. He doesn't
think after examining the knee and having him perform certain tasks that he has damaged any tendons. He has all the symptoms of rheumatiod arthritis. He is very athletic and plays competitive sports and we are praying that his knees are not permanently damaged by this drug. Parents please research all drugs and there side effects before giving them to your children! Doctor's DO make mistakes!! The pharmacist failed us too.