Synovitis fluid in baby hips usually takes 2 weeks to several months to clear up and may be affected by the type and severity of the disease. Common causes of synovitis fluid buildup in babies include aseptic inflammation of the hip joint, or synovitis can be caused by infection with bacteria or tuberculosis. For aseptic synovitis of the hip joint, the fluid can usually be absorbed by itself in 2 to 4 weeks after the onset of the disease, and for bacterial or tuberculosis infection, it usually takes a few weeks to a few months to get better. The more severe the infection and the more time it takes for the synovitis fluid to clear up, the longer it will take. When your baby develops a hip joint effusion, he or she should go to a regular hospital and be treated under a doctor’s supervision.